Tsukasa Yugi

He's a supernatural entity,else a ghost,a dead body.
he's older brother Amane/Hanako-kun killed him at the age of four, meanwhile he appeared older at the anime.

Tsukasa Yugi from Toilet-Bound Hanako-kun is a deeply chaotic, manipulative, and childish, yet highly dangerous, supernatural entity. He alternates between a cheerful, affectionate demeanor—especially regarding his twin brother, Amane (Hanako)—and a ruthless, psychopathic lack of remorse, characterized by extreme violence, disregard for rules, and a desire to cause chaos. Childish yet Cruel: He displays an innocent, bubbly exterior but can immediately switch to unsettling aggression and cruelty. He shows no remorse for violence, exemplified by his reckless actions and glee in causing harm.
Obsessive Brother Complex: Tsukasa adores his older twin brother, Amane. This attachment is extreme and often described as a "brother complex," with his actions frequently aimed at getting attention from or playing with him.

Appearance: Small stature, choppy black hair, wide, constantly constricted amber eyes, and two small fangs.
Outfit: Typically wears a white Western shirt under a black kimono, a grey hakama, red ankle-height socks, black shoes, and a hat similar to Hanako's.
Yorishiro Seal: Features a black seal (talisman) with the red kanji 封 (seal) on his right cheek.
Supernatural Companions: Accompanied by two black, fish-like spirits called kokujoudai (black haku-joudai) with pink and blue markings.

Jibaku Shounen Hanako-kun Wiki
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Differences from Hanako:
Seal Placement: Tsukasa’s seal is on his right cheek, while Hanako's is on his left.
Eyes: Tsukasa's eyes are always constricted, giving him a more intense, chaotic look.
Outfit: While often wearing a similar uniform to his first appearance, his main outfit is a distinctive black kimono-style Shosei uniform.
Companions: His spirits are black, while Hanako's are white.

As a human, he appeared exactly like his twin, Amane. He is often seen with a smile, regardless of how chaotic or cruel his actions are.