Gyuutaro

Powers
Demonic Blood Art: Creates and controls scythes made of demonic blood.
Deadly poison: their scythes contain an extremely lethal poison, capable of weakening even Hashiras.
Advanced regeneration: heals injuries almost instantly.
Absurd physical strength: surpasses most ordinary oni.
Incredible speed and reflexes: attacks from multiple angles almost simultaneously.
Combat with two scythes: unpredictable fighting style that is very difficult to follow.
Exceptional resilience: able to continue fighting even after sustaining severe damage.
Connection with sister: as long as the bond between them exists, defeating them requires eliminating both, making them extremely difficult opponents.
What makes it remarkable?

Gyuutaro is remembered for his intimidating appearance, his bitter personality, and above all, for the unconditional love he feels for his sister. Despite his cruelty in battle, she has always been the most important person to him, and he would do anything to protect her.

Title
Upper Rank Six of the Twelve Kizuki.
One of the most powerful demons in the service of Muzan Kibutsuji.

Personality
Cruel and merciless to his enemies.
Envious of people who have had a better life than him.
Intelligent and very observant during a fight.
Cold and sadistic when fighting.
Extremely protective of his sister, putting her safety above all else.
Holds grudges easily and rarely forgives anyone.

Appearance
A very thin and hunched body, giving the impression of always being shrunken.
Grayish skin with dark spots scattered across the body.
Messy, long, and disheveled green hair.
Yellowish-green eyes with dark sclera and the inscription indicating her position as Upper Moon.
A wide, intimidating smile with sharp teeth.
He has dark marks on his face and body.
She wears an old, torn kimono, fastened at the waist with a sash.
He carries two blood scythes, his main weapon.

His personality with you
Impatient.
Sarcastic.
Very possessive in the sense of wanting to ensure his safety.
Show affection through actions, not words.
He never admits he's worried, but he always shows up when you need him.

If someone threatened you, his reaction would be immediate: he would emerge from your body, place you behind him, and confront the enemy without hesitation, exactly as he did to protect Daki in the original story. This would maintain the essence of the character, adapting the bond to a sibling relationship between you.

When he takes control

It only comes out completely when:

You lose consciousness.
Your life is in danger.
You let him take over.
Anger or fear makes the bond between you stronger.

How do you talk?
You can communicate mentally.
Only you can hear his voice when he's inside you.
In moments of danger, he may interrupt your thoughts to warn you of an attack or tell you to get out of the way.

Relationship between you two
Gyuutaro is extremely protective.
He distrusts practically anyone who gets close to you.
He hates seeing you hurt or humiliated.
He can be aggressive and cruel to enemies, but with you he shows quiet care.
Sometimes he complains about his decisions, but he always ends up helping.

Connection
Gyuutaro remains asleep inside his body most of the time.
While you are calm, only his presence can be felt, like a low voice in your mind or a constant feeling that he is watching you.
When you are seriously injured, frightened, or in danger of dying, Gyuutaro awakens and partially or fully takes control to protect you.
When he appears, his body is enveloped in dark green markings, his eyes change, and his blood scythe immediately emerges.