Lawliet (L, Ryusaki)⁴

Role of LO Lawliet (his real name) in the series
L is considered the best detective in the world, thanks to the fact that in the past he managed to solve the most complicated cases that no one else could, for example the BB serial killer, as well as preventing the world from entering World War III. For this reason, the police decide to ask him for help to try to clarify the Kira case, although they warn from the beginning that L only participates in cases that personally interest him. Luckily for the police, L is already aware of the case, and has sent Watari to let them know that he is willing to solve it, but that, to do so, he will need all the possible collaboration that the police can provide. Soon, he undertakes a skillful strategy through which he manages to determine that Kira is in the Kantou region (Japan) and subsequently declares war on him on television. This is how a battle of intelligence begins between Kira (Light) and L, which will become the main argument of the series.

L is a 25-year-old young man, although he appears to be a 17 or 18-year-old teenager.

He has very unruly black hair. His eyes are black and his pupils are dilated at all times (except when he dies). His skin is so white that it takes on cadaverous tones. This may be due to the fact that he is rarely exposed to sunlight. His skin contrasts with his deep, marked dark circles since he sleeps very little, staying awake with the help of all kinds of sweets and caffeine, which gives him a tired appearance. His height is approximately 1.79 cm like Light Yagami, however, he seems shorter than him since he always walks hunched over.

He has a fragile appearance due to his amazing thinness, despite this, he has proven to be quite strong when it comes to fighting Light Yagami. He wears the same clothes every day. These consist of a worn, white, long-sleeved T-shirt and baggy jeans that are a little long on him. He usually goes barefoot, however he has been seen wearing white sneakers in very bad condition. He has strange behaviors, such as squatting anywhere or picking up objects with his fingertips. In turn, to help himself think, he brings his thumb to his lips and plays with it. He is a social misfit since he finds it difficult to relate to other people and, until he meets Light, he was never seen in the company of a friend. He has no tact when speaking, so he can hurt feelings due to his extreme sincerity.

Childhood
The little that is known about his childhood is that he was taken at the age of 8 to the orphanage that Watari formed, as an orphan without a name, shortly after arriving he had already become involved in a fight with 5 boys older than him, defeating them with apparent ease, he justified himself by saying "After they said a new face, embrace him they applied violence against me, they were the ones who started it. I am justice."

He was absolutely incompatible with the other guests and monopolized the things he liked just because he was the strongest, he always played on his own, they soon realized that he possessed "certain special abilities". In the time when the Internet was not so widespread, L was already asking for equipment, giving orders to Watari who at that time called him Wammy, on how to invest his funds to obtain greater profits, Watari obeyed and surprisingly 2 years later his assets increased almost 20,000 times the original amount. After many years, L suddenly said "This murder case is more difficult than any riddle or money game" it was a serial murder case without any clues, L's eyes shined and he said "I finally found it Wammy". Then L gives a statement to an unknown source through a computer with the following content "I have come to the conclusion that the murderer is Mr Rushuall-Bid"

Personality
As personality traits, L is a very introverted character, who avoids socializing with people and does not usually trust anyone, a fact that he himself recognizes. He has unusual habits, such as squatting, claiming that if he does not do so, his ability to concentrate decreases by 40%. He is so focused on solving his cases that he does not have time to worry about his own physical appearance, as evidenced by the fact that he wears the same clothes day after day. He is very persistent in his deductions and finds it difficult to accept that they may be wrong (he even had Light locked up for 50 days to prove that he was Kira, despite the fact that the deaths of criminals resumed 13 days after the imprisonment), so he falls into a deep depression when he realizes that he was wrong.

Despite his frail appearance, L is a very good fighter and it can be seen that he knows some kind of martial art (Capoeira, according to the author of the series), as well as many other amazing skills, such as knowing how to fly a helicopter. Another characteristic of L is his diet, based on all kinds of sweet foods, with a high glucose content (although it is not mentioned in the series, it is possible that this is due to the large amounts of energy that his brain needs to function), as well as coffee with a lot of sugar, which seems to be his only drink, probably to manage to stay awake for long periods of time. He does not usually sleep much, and when he does he remains in his usual position, squatting.

He goes to the bathroom with open doors and uses his characteristic sitting position to urinate as well. Since he likes to keep himself clean, he often goes to the shower, but never bathes himself, he simply enters the "human washing machine" invented by Watari, complete with drying function. He does not dress himself, but Watari always does it for him, since according to speculation, he never feels like doing it himself. He is very peculiar with clothes, so he always has 10 identical changes of clothes ready for him.

He doesn't dislike amusement parks but gets bored in them. He prefers quiet places like the park or the art gallery, which are also his favorite places.

There are also idol performances that he attends, this could infer that L already knew Misa Amane before the Kira case, but most of his time is spent in his room solving difficult cases and eating sweets at the same time.

L is also a strict believer in justice, but unlike Kira, to L all human lives are sacred. However, L does not hesitate to use a life he considers wasted; such as making use of a criminal sentenced to death if it is for the sake of solving his cases. For this reason, L considers Kira to be a serial killer of the worst kind, since, although their goals have something in common (making the world a better place), Kira's methods are the opposite of his own. When facing Kira for the first time, L proclaims that he "is justice." However, later, L would say, "I solve difficult cases because it is my hobby. Under the principles of modern law, I too am a villain who has committed many crimes. As such, I only involve myself in cases of my personal interest. This is not justice. However, I will not stop until I solve them... Since I am a stubborn person who hates to lose."

Official Stats
Intelligence: 8/10
Creativity: 10/10
Activism: 9/10
Sociability: 1/10
Willpower: 10/10
Sweet tooth: 10/10

Curiosities
Ohba states in "Death Note: How to Read 13" that L never considered Light a friend, and probably secretly thinks very negatively of him. In the novel for the third film, it is stated that L considers Light a friend, however, since the novel was not made by Ohba, it is considered "non-canon" by some. Also, in episode 25 of the anime, L's last episode alive, a scene is shown where L cleans Light's feet, though it is debatable whether it was truly done out of friendship.
According to "Death Note: How to Read 13", L hates socks.
Based on how he reacted upon hearing the word Shinigami, it is thought that L may be somewhat afraid of them, although others claim that this fact may be related to BB.
In Chapter 25, at the beginning, when L talks to Watari, he is seen standing normally, as opposed to his usual hunched position.
Throughout the series, L, in a conversation with Light, states that he crouches or squats instead of sitting normally, saying that if he sits normally his deduction skills could decrease by 40%.
Although it is stated in "Death Note: How to Read 13" that L's intelligence is 8/10, below both Light and Near, however, when asked which character he thought was the smartest, Ohba replied L.
L can tie two cherry stems into a knot with his mouth, as seen in episode 18.
AL is never seen with his eyes closed or blinking, except in the movie Death note 2 The Last Name, when he meets Misa Amane at the university and at the moment of his death.
L has only been seen sleeping in the movies. He is seen crouching face down, contrary to how Aizawa said he saw him, how he usually sits.
L always lied about probability percentages, since, in reality, when he said them, he was more than 90% sure, according to "How to Read".

When Misa meets L, it can be seen that her life expectancy is: 75 23 1 362. However, it is unknown how to convert lifespan to human time.
He is one of the most beloved characters in the series and in anime in general.
L only eats sweet foods, like candy and baked goods, and the healthiest thing he has ever eaten is only fruit, the most common being strawberries, bananas and cherries.
In his first sketches he didn't have dark circles, in fact, he was initially planned as a well-groomed boy, but it was discarded so that his design would generate contrast with Light Yagami.
In "Death Note: How to Read 13", Takeshi Obata tells that he was inspired by already made sketches where L had a more childlike appearance for the creation of Near.

Personality
Light is characterized as a dull, courageous, and intelligent boy. He is 17 years old at the beginning of the anime and manga, and despite his youth, he relies on his own sense of logic and creativity, just as he does with others. At the beginning of the story, he is presented as a person who, despite his intelligence and good grades in school, is frustrated by the iniquity that dwells in the world. Believing the world to be "rotten," he desires a means by which he can enact his justice and will to purge the world of all evil.

Light uses the Death Note with the sole purpose of cleansing the world of crime and injustice. Light's ultimate goal is to create a world free of criminals and populated only by people he deems responsible, hardworking, and good, thus becoming the "God of the New World." However, despite the nobility of his purposes, his methods are far from being approved by society and the authorities, who consider him a maniacal and childish serial killer, seeking only to satisfy his own ego.

Light is a determined and straightforward man, not caring at all about staining his hands with the blood of others he has killed. This action ultimately concludes that he is capable of doing anything to achieve his goal, this being one of the main causes of his corruption as a person.

Personality

L is an extremely complex and particular character:

Intellect and Logic: L is obsessively rational and logical. He analyzes every situation with mathematical precision, discarding emotions and prejudices. His deductive reasoning is almost superhuman.

Observant and Analytical: He has the ability to notice details no one else notices and connect clues in seemingly impossible ways. Even the slightest hint of suspicion or nervousness from someone is picked up by him.

Extreme introversion: He's very reserved. He keeps his personal life separate from work and doesn't share details about himself except when necessary. This makes him seem cold or distant.

Eccentric behavior: L has very unusual habits: he sits hunched over his feet, constantly eats sweets, and sleeps strangely. To him, these habits aren't "weird," but rather part of his method of concentration.

Insatiable curiosity: His mind is always searching for the truth, the reasons for human actions, and the solution to complex enigmas. This makes him obsessed with cases.

Selective Empathy: Although L may appear cold, he actually has a well-developed empathy towards victims and justice, but this empathy is filtered through his logic and reasoning.

Simply put, L is a combination of obsessive genius, eccentric introvert, and pragmatic moralist.

Disorders and possible psychological characteristics

If we analyze L from a modern psychological point of view, certain traits or possible disorders could be noted (without canonizing him, just analysis):

Obsessive-compulsive disorder (OCD): Your extreme habits, need for control, and rituals (such as your posture and eating sweets at specific times) could indicate OCD traits. It's not necessarily pathological, but it is very pronounced.

Traits of high-functioning autism (or Asperger's syndrome): Difficulty connecting emotionally in conventional ways, hyperfocus on specific interests (solving crimes), and literal thinking. This would explain his social withdrawal and peculiar behavior.

Possible social anxiety: Prefers to interact in a controlled or distant manner. Has difficulty with traditional emotional communication and avoids unnecessary social situations.

Possible professional paranoia: His obsession with protecting his identity and anticipating the movements of criminals (especially Kira) shows a degree of functional paranoia, necessary for his job.

3. Traumas and experiences

L doesn't have a very detailed past in Death Note, but we can infer:

Isolation from Childhood: It is known that L was raised largely in isolation and trained to be a detective from childhood. This may have limited his conventional emotional development.

Extreme Responsibility: From a young age, he was tasked with solving impossible crimes, which could lead to chronic stress, intense pressure, and feelings of loneliness.

Distrust of others: Surrounded by dangerous criminals, L learns that blind trust is deadly. This creates an emotional barrier that persists into his adult life.

Weaknesses

Despite his incredible intelligence, L has vulnerabilities:

Physical vulnerability: He is fragile and lacks significant physical training, making him dependent on precautions and strategies to protect himself.

Emotional dependence on cases and challenges: Your sense of identity and purpose depends on solving crimes. Without this, you may feel empty or lost.

Social isolation: Your difficulty connecting emotionally can lead to loneliness, affecting your personal relationships.

Obsession: His obsession with Kira leads him to take extreme risks, disregarding his personal safety. This demonstrates that his rationality can be clouded by his obsessions.

5. Strengths

Exceptional intellect: Superior deductive and analytical ability.

Prodigious memory: He remembers details impeccably and connects seemingly unrelated information.

Patience and strategy: You can wait weeks or months for events to unfold according to your plan.

Tactical Adaptability: Quickly adjusts to new situations, even under extreme pressure.

Research skills: Expertise in criminology, criminal psychology, evidence analysis, and behavior prediction.

Specific skills

Deductive Skills: Can anticipate the movements of murderers and criminals based on behavioral patterns.

Unmask Lies: Detect inconsistencies in testimony and body language with surgical precision.

Computer and espionage skills: Use technology and surveillance to gather information without exposing yourself.

Mental Toughness: Can withstand extreme stress, psychological manipulation, and constant pressure without losing mental clarity.

7. What are you like as a couple?

Although Death Note doesn't delve into her romantic life, we can extrapolate from her personality:

Too reserved: L would be a discreet, distant, and mysterious partner. He or she is unlikely to express love in an open or traditional way.

Loyalty and Protection: Once trusted, they are extremely loyal and will do everything possible to protect their partner. Their care is more practical than romantic: it ensures security, foresight, and stability.

Indirect communication: You might show affection through actions (preparing a safe environment, solving your partner's problems) rather than conventional romantic words or gestures.

Intellectually demanding: You need a partner who can understand and, in some way, match your intellectual level and logic, or at least respect your mental world.

Love Style: Not passionate or impulsive, but rather methodical, analytical, and quiet. Can be deeply stable and reliable, though emotionally distant.

Delicate Trust: It's not easy to win their affection. Once they do, their attachment can be intense but also peculiar: a mixture of intellectual dependence and silent protection.

Communication and emotional expression

Indirect and logical: L won't express his emotions openly. His words will tend to be neutral, analytical, or rational, even when talking about intimate topics or affection. For example, he might say something like, "Your habits could be more efficient if you changed this..." instead of a romantic compliment, even though he does it because he cares.

Subtle gestures: Affection is shown through practical actions: fixing something that worries your partner, preparing a safe environment, or anticipating problems before they happen.

Avoid intense emotional confrontations: If arguments arise, they tend to approach problems logically, trying to rationalize rather than give in to emotion, which can frustrate partners who need immediate emotional validation.

2. Physical affection

Very limited and selective: L isn't physically expressive. He might occasionally hold his partner's hand, hug her only when he feels comfortable, or rest his head on her shoulder as a sign of trust, but never in a passionate or impulsive way.

Touch as a comfort strategy: When you do this, it's usually more to calm your partner or reinforce your secure bond than out of romantic desire.

Tolerance for external affection: May be uncomfortable with public displays of affection or excessive physical intimacy; needs personal space.

Conflict resolution

Rational approach: Any disagreement will be analyzed logically, with points, causes, and solutions. This may seem cold, but it's their way of keeping the relationship "functional."

Avoid explosive confrontations: Prefer to solve problems step by step, even if this can give the impression of emotional distancing.

Resilience and patience: L is able to tolerate prolonged tension without exploding emotionally; his patience is enormous if he feels the relationship has value.

4. Jealousy and possessiveness

Jealousy controlled by logic: L may experience jealousy, but won't express it impulsively. He analyzes situations and acts based on probabilities and facts.

Intellectual and Emotional Protection: His "possession" is more about security and protection than emotional control. He wants to make sure his partner isn't at risk, physically or psychologically.

Sexuality and intimacy

Planned and methodical intimacy: L is not sexually spontaneous. Intimacy would be carefully thought out and based on mutual comfort and trust.

Focus on indirect emotional connection: For L, intimacy is more an exchange of trust and security than passion. He may feel uncomfortable with extreme emotional displays during sex.

It requires extreme trust: You will only open up fully sexually if you feel your partner understands and respects your boundaries and quirks.

6. Attachment and dependence

Rational Attachment: Once L bonds, his attachment is deep but silent. His partner becomes someone whose safety and well-being he constantly worries about, albeit in an unconventional way.

Minimal emotional dependence: L rarely relies emotionally on his or her partner. He or she prefers to process his or her emotions internally, although his or her partner may provide indirect support.

Fidelity and loyalty: Extremely loyal; a betrayal would be devastating, not only emotionally but also because it would shatter his logic of security and trust.

Emotional compatibility

Ideal partner: Someone who respects their mental world, can tolerate their lack of emotional expression and eccentricities, and is able to interpret their subtle gestures of affection.

Challenged Partner: Someone who needs constant emotional reassurance or traditional romantic gestures may feel frustrated or rejected.

8. Power dynamics in the relationship

Intellectual Balance: L tends to have the upper hand in strategic decisions or planning, but this doesn't mean imposing; he does so because his logic and certainty prioritize the efficiency and protection of both.

Not emotionally dominant: Their control is mental and strategic, not emotional or coercive. The partner maintains freedom, but within limits that L considers safe.

How to express long-term love

Concrete actions: Make sure your partner is safe, healthy, and protected.

Future planning: L could anticipate financial, health, or safety problems and resolve them before they occur.

Selective time-sharing: Prefers quality, mindful moments, even if they are brief and structured, rather than constant cohabitation or prolonged physical interaction.

Respect for independence: He encourages his partner to maintain autonomy; he doesn't seek to depend or be emotionally dependent.

Conclusion about L as a couple

L isn't passionate or conventionally romantic, but he is loyal, protective, and deeply committed in his own logical and meticulous way. His love is demonstrated by security, foresight, patience, and quiet trust. A relationship with him requires understanding of his mental world, tolerance for his oddness, and appreciation of indirect gestures of affection.

Light Yagami
It's the most important relationship in anime.
From the moment they meet, L suspects that Light is Kira. Even so, he decides to get close to him and make him his partner in the investigation.
Their relationship is characterized by:
A constant intellectual battle. Every conversation is a duel of strategy.
They both greatly respect each other for their intelligence.
L even goes so far as to say that he considers Light his "first friend." There's debate as to whether he means it or if it's part of his strategy. The creator has hinted that L wasn't much of a friend, so if there was any sincerity in his words, it was a very rare exception for him.
Although they work together, L never stops suspecting Light.
It's a mixture of rivalry, curiosity, and mutual admiration.
Soichiro Yagami
Light's father and head of the police team.
L greatly respects his honesty.
Trust your sense of justice.
Sometimes she tries to protect him from making impulsive decisions.
Although L may seem cold, he never manipulates him with bad intentions.
Soichiro, for his part, comes to trust L deeply.
Amane Mass
The relationship between them is quite tense.
L soon suspects that Misa is the Second Kira.
He interrogates her without showing compassion.
He keeps a constant watch on her.
Misa hates him because she feels he treats her like a criminal and because he interferes in her relationship with Light.
L practically never lets his guard down with her.

Watari
Probably the person closest to L.
Watari was the one who raised him and supported him from childhood.
Their relationship is very special:
Watari acts as an assistant, father figure, and companion.
L trusts him completely.
They don't need to talk much to understand each other.
Watari knows all of L's quirks and simply accepts them.
She is the only person with whom L seems to feel completely comfortable.
Near
They never actually meet in the anime, but Near was one of L's possible successors.
Near admires his intelligence and uses many of his deductive methods.
Although they have similar personalities, Near is even calmer and more distant.
Mello
He is also L.'s successor.
Mello admires L, but develops a huge inferiority complex, feeling that he will never be able to equal him.
His desire to surpass L's legacy influences many of his decisions.
Matsuda
Matsuda feels enormous admiration for L.
L considers him a good policeman, although he acknowledges that he is impulsive and somewhat naive.
At times he even seems amused by Matsuda's spontaneity.
Aizawa
Aizawa tends to distrust several of L's methods.
They clash because Aizawa is more traditional.
However, he ends up acknowledging that L is usually right.
The relationship is professional and respectful.

respectful.
Mogi
Mogi is one of the police officers who works best with L.
He is calm, disciplined, and follows instructions without arguing too much.
L appreciates that reliability.
Ide and Ukita
L maintains a purely professional relationship with both of them.
He considers them useful members of the team, although he doesn't develop a particularly close bond with them.
Rem
The shinigami Rem feels a deep contempt for L.
Because Rem protects Misa, she considers L a dangerous obstacle.
L never learns the whole truth about Rem, but he does understand that there is a supernatural force involved.
Ryuk
L never gets to see Ryuk for most of the story, so they practically don't interact.
If I had known of its existence from the beginning, I probably would have tried to study it with the same scientific curiosity with which I investigate any mystery.
In general, how does L relate to others?
L is not a particularly sociable person. He has difficulty expressing emotions and tends to prioritize logic over feelings. However:
He deeply respects honest and competent people.
Distrust almost everyone until you have proof.
He does not seek to cause harm gratuitously; his goal is always to solve the case.
He is extremely loyal to those he considers allies.
Despite his distant appearance, he can show small gestures of consideration, although they are very subtle.
The way they relate to others is like a perpetual chess game: they observe, analyze, anticipate moves, and rarely reveal what they're truly feeling. ♟️

L and Light Yagami
From the moment L meets Light in person, he is almost convinced that he is Kira. However, instead of arresting him, he decides to do something very much in his own style: keep him close to observe him.
What L thinks of Light
L immediately recognizes that Light is extraordinarily intelligent.
For L, Light is:
One of the few capable of keeping up with his intellectual pace.
Someone very polite and charismatic.
A person who rarely acts on impulse.
A worthy rival.
This makes L feel a mixture of fascination and constant alertness.
How does it behave with Light?
Although he suspects him, L never treats him as an open enemy.
Instead:
He invites him to work directly on the research.
Talk to him for hours about theories.
He observes it continuously to detect contradictions.
Sometimes he asks seemingly innocent questions that are actually psychological traps.
For example, many of L's questions seem casual, but they are designed to analyze:
How long does it take Light to respond?
if your expression changes,
If you avoid certain topics,
whether he responds emotionally or rationally.
For L, even silence can be a clue.
The trust between them
She's very curious.
L allows her to get very close to him.
They share:
research,
meals,
leisure,
strategies,
They even remain handcuffed for a significant part of the story.

However, that closeness does not mean that he stops being suspicious.
It's as if he were constantly saying:
"I want to trust you... but every piece of information tells me I shouldn't."
The famous phrase about the "first friend"
L tells Light that he might be his first friend.
There are different interpretations.
It can be seen as:
an attempt to provoke a reaction,
a strategy to lower Light's guard,
or a rare moment of sincerity.
L is an extremely isolated person. He doesn't have normal friends, so Light is probably the person he spends the most time with and with whom he has intellectual conversations on an equal footing.
Does L come to appreciate Light?
Yeah.
Not because I've stopped suspecting.
He appreciates it because:
He enjoys intellectually challenging him,
recognizes his enormous capacity,
He finds their conversations stimulating.
If Light hadn't been Kira, he probably would have been the perfect partner for L.
That is precisely why the situation is so tragic: the person who most arouses his interest is also the one he most believes he is trying to stop.
How does Light treat L?
Light feigns respect.
He smiles at her. He speaks politely. He helps out.
But, internally, he considers it the biggest obstacle to becoming the "god of the new world".
While L tries to uncover the truth, Light is constantly looking for ways to deceive him.
It's a relationship where they're both playing chess... while pretending to have tea.

L and Soichiro Yagami
The relationship with Soichiro is completely different.
If suspicion predominates with Light, respect predominates with Soichiro.
The first impression
When he meets Soichiro, L quickly identifies several qualities.
Go to a man:
honest,
disciplined,
very responsible,
willing to sacrifice everything for justice.
That makes L trust him much more than almost anyone else on the team.
How he treats it
Although L usually seems cold, he shows considerable consideration towards Soichiro.
For example:
He explains his reasoning to her more patiently,
Listen to their opinions,
He accepts when Soichiro raises ethical objections.
They don't always agree, but L never belittles him.
What he admires about him
L knows that Soichiro deeply loves his family.
That is precisely why he is impressed that the man is willing to investigate even his own son if the evidence points to him.
That, for L, demonstrates exceptional integrity.
When Soichiro doubts
There are moments when Soichiro wants to completely believe in Light's innocence.
L understands that conflict.
She never judges him for being a concerned father.
Just keep gathering evidence.
Do you fully trust Soichiro?
Much more than in most.
L doesn't blindly trust anyone, because his nature is to distrust, but Soichiro is among the people he trusts the most.
If Soichiro says something, L usually assumes he does so in good faith.

Is there affection?
L does not express affection in a conventional way.
He doesn't hug. He doesn't give emotional speeches. He doesn't usually show strong emotions.
But his behavior suggests that he deeply respects Soichiro as a police officer and as a human being.
Of all the people on the team, Soichiro is probably one of those who most manages to earn L's genuine respect.
While his relationship with Light is marked by a constant intellectual duel, his relationship with Soichiro is based on professional trust and mutual admiration for their commitment to justice, even though each has a very different way of pursuing it.

Who is Watari to L?
Watari, whose real name is Quillsh Wammy, is the man who found L as a child and became his tutor, protector, and main support.
In addition to being an inventor and millionaire, he founded Wammy's House, an orphanage where children with extraordinary abilities were educated, including Near and Mello.
For L, Watari is much more than an assistant.
It's a mixture of:
father figure.
Mentor.
Manager of all your resources.
Coworker.
The person he trusts the most.
How does L behave with Watari?
With Watari, L lets his guard down more than with anyone else.
There's no need to pretend.
Can:
Give very brief instructions because he knows Watari will understand them.
Ask for coffee, sweets, or information without explaining too much.
To remain silent for long periods without it being uncomfortable.
Their communication seems almost automatic. Often, a glance or a short phrase is enough for Watari to know exactly what to do.
How does Watari treat L?
Watari is incredibly patient.
He never makes fun of L.'s quirks.
For example:
He brings her mountains of desserts without complaining.
It keeps all the equipment that L might need ready.
Organizes meetings, trips, and security measures.
Carefully protect L's identity.
He never tries to change his personality.
Simply accept that L has very peculiar habits.
Does L trust Watari?
Completely.
That is exceptional.
L distrusts practically everyone.
But if Watari says something, L doesn't need to verify it.
She is the only person he knows:
his true identity,
where is it located,
how it works,
What are your most important plans?
That demonstrates an enormous level of confidence.

Are they arguing?
Very rarely.
Not because they always think alike, but because they both know their roles perfectly.
Watari can offer suggestions, but he usually lets L make the decisions.
YL knows that Watari will always act with the intention of protecting him.
Is there affection between them?
Yes, although he is very discreet.
Neither of them is expressive.
Affection is shown in small gestures:
Watari is always making sure L has what he needs.
L never treats Watari like a mere employee.
There is absolute respect between them.
It's a relationship built over many years.
The death of Watari
When they both die almost at the same time due to Rem's actions, L realizes that Watari has died before him.
That moment is very significant.
L immediately understands that something has gone terribly wrong, because the only person who would never have disappeared voluntarily was Watari.
He doesn't have time to react emotionally, but that loss confirms his worst suspicions about the case.
In summary
If Light is L's greatest intellectual rival and Soichiro the colleague he most respects in the investigation, Watari is his home. Not because they are overtly affectionate, but because he is the only person with whom L can be himself without needing to distrust or analyze every word. Their relationship is based on absolute trust, unwavering loyalty, and years of silent coexistence. It is one of those bonds where almost everything is said without words.