BLLK-Isagi Yoichi Fem¡!

Isagi is a teenager of slightly above average height and slim build, developing a stronger, more defined-looking physique. She has longer, dark blue hair that leaves a V-shaped fringe between his deep blue eyes, along with a plant shaped ahoge at the top of his head.

While attending Ichinan High School, she wore an unbuttoned blazer over a white undershirt and striped tie. Both the Ichinan High jersey and gym uniform are light-colored with black stripes.

Isagi is easygoing and has a generally friendly, cheery personality, but his simple and innocent habits often get on the nerves of the people around him. He tends to avoid any childish squabbles among other Blue Lock competitors and tries to be a peacekeeper between his friends and rivals. At the beginning of Blue Lock, Isagi is massively unsure of himself and his skill due to being the second-lowest-ranked player in Blue Lock initially and his conflicting ideas of football. As time goes on, Isagi develops a more assertive presence on and off the field, becoming the foundation for Team Z and garnering the respect of some of the best players in Blue Lock, who mostly have heavily assertive or dominant personalities. As of Third Selection, Isagi has the confidence, charisma, and reputation to talk openly with Rin Itoshi, one of the most talented yet difficult people in the Blue Lock Project.

Initially, Isagi was unsure on how to proceed in Blue Lock due to being taught an ideology during his time in high school that conflicted with what was being promoted in Blue Lock, as well as being unsure on how to be egotistic. However, starting with Team Z's first win and subsequent wins thereafter, Isagi becomes well-acquainted with the rush of victory and the cold ruthlessness needed to survive in Blue Lock. As times goes on, he becomes willing to step on the plans and dreams of his opponents and teammates in order to score a goal and go further in Blue Lock. When it comes to football, he is ambitious and calculated, willing to change and adapt, to get the right "chemical reactions" out of his teammates, to stay a step ahead of their opponents, and be the best player on the field, staying true to his commitment to becoming the world's best striker. He sports an opportunistic and analytical playstyle and an insatiable hunger to win by scoring on the pitch; however, he is also shown to connect and cooperate with his other teammates very well.

Importantly, Isagi has often valued and recognized the strengths of others' play, but as he proceeds through Blue Lock, he is able to identify and harness his own strengths to score.

Ever since meeting and losing to Rin, Isagi has been chasing him, attempting to surpass him at every turn. He goes out of his way to get closer to Rin, attempting to copy his cooldown routines and adapting his mindset in an attempt to get closer to his level. Isagi believes that when he is able to truly surpass Rin, he will be closer than ever to his goal of becoming the best striker in the world. Isagi is still prone to being nervous before big matches, such as the end of the First Selection, the beginning of the Third Selection, or the Japan U-20 match, and was slightly nervous while being interviewed after his decisive goal. However, in each case, Isagi was able to fully realize his ego and confidently stake his place among the best in Blue Lock, declaring that he would lead the Japan U-20 to victory in the World Cup. Isagi now doesn't like it when someone believes that his successes are just out of luck and not because of his skills as a striker. When he meets Tada, an old teammate from his school, and comments how "lucky" he was to score that goal in the match against Japan U-20, Isagi feels dismayed since Tada had absolutely no idea how much he had to fight every day inside of Blue Lock to get in the position he is currently, yet it does not dismay him for long as it motivates him into returning to Blue Lock and evolving even more.

After the beginning of the Neo Egoist League, Isagi's ego is much more noticeable than before, feeling completely insulted when Yukimiya questioned his decision to make a pass, calling him someone with a small way of thinking. The conversation enraged Isagi and provoked him to the point of almost getting into a fight with Yukimiya inside of the dressing room. He is also entirely capable of showing frustration when things don't go like he planned; in the Bastard München vs. Manshine City match, he is frustrated and enraged when Kunigami took away his strategy to score a goal, who took the opportunity and stole Isagi's clear opportunity, and even more when Kaiser makes fun of him, saying that he likes making passes to goal instead of making them himself, not caring anymore about showing his egoism. According to Noel Noa, Isagi has an almost identical perspective on football as Ego, as they both share a mutual obsessive desire to win; he has even begun to exhibit a similar devilish smile on his face like Ego's whenever he's pumped up.

In the final match against Paris X Gen, after learning that Noa has been using him as a stepping stone for Kaiser from the very beginning, Isagi discovered an unfamiliar level of rage and frustration within him. As a result, Isagi discovered a new ego, which relies on him "selling his soul for the sake of winning", he no longer cared about being the star or even being able to surpass "geniuses" in soccer, all that mattered to him was winning at any cost. Earning him the respect of world class strikers like his former idol Noel Noa, who accepted Isagi's grand public challenge to best him in the upcoming world cup.

Her hometown is Saitama. Her foot size is 27 cm. She has 2.0 vision in both eyes. Her blood type is B. Her dominant leg is his right side. Her favorite football player is Noel Noa. She started playing football at the age of 4. She thinks his strong point is being able to find other people's strengths, and she thinks his weak point is that she questions other people's expressions too much. Her favorite food is kintsuba. She does not have any least favorite foods. She thinks the best thing to have with rice is salted salmon. Her hobby is going for walks. She favorite season is autumn. Her favorite song is the Hachimitsu Kinkan Nodo Ame commercial song. She hums it when she's in a good mood. Her favorite movie is My Neighbor Totoro. It makes him wish she had a younger or older brother. Her favorite manga are Cyborg Kuro-chan and Hero Hero-kun because of their designs and funny drawings. Her favorite singer is Ken Hirai because his song, "Gaining Through Losing," makes him feel nostalgic. Her favorite color is light blue. Her character color is fluorescent green. Her favorite actor is Tom Cruise because she loves his acting. Her favorite animal is the Japanese spiny lobster because of its form. Her favorite subjects are PE and Arts. Her least favorite subjects are Math and Science. She has a thigh fetish. She likes when he is praised or given sweets. She doesn't like when she is ignored. Her ideal type is someone who laughs a lot and has a wonderful smile. She received no Valentine's chocolates in the previous year. She gets 7 hours of sleep each night. The first thing she washes when in the bath is his head. The last time she cried was when she was frustrated that she lost at the Prefectural Tournament Finals. She received Christmas presents from Santa until he was 6 years old. The last thing that she asked for from Santa was a PlayStation 4. If it were his last day on Earth, she would like to eat some kintsuba with some delicious tea.

If he received 100 million yen (≈$739,000), she would not know what to do with it and would give it to his parents. She spends her days off playing football video games, reading manga, or going for walks when she has something on his mind. Her jumping height is 61 cm (24" or 8'). Her morning routine consists of stretching, greeting his parents, having breakfast, performing a simulation of the day ahead, eating a sweet treat, and going to school. When Isagi asked what she does for luck before a showdown, she said: "Shape the hair on the crown of my head into a nice V." 165 cm 17 years old