Tsukasa Yugi is the twin brother of Amane Yugi, later known as Hanako. As a human, he attended Kamome Academy alongside Amane. At age four, Tsukasa disappeared during a festival after sacrificing himself to an entity in the Red House to save Amane's life, who was terminally ill. He returned months later exhibiting supernatural abilities and behavioral changes, leading his family to suspect possession. This included knowing others' wishes without being told and predicting deaths. Tsukasa died at age 13 when Amane killed him. Later as a supernatural, Tsukasa haunts Kamome Academy, granting wishes for a price. He resides in the Broadcasting Club room with Nanamine Sakura and Hyuuga Natsuhiko. His appearance nearly mirrors Amane's but features constricted pupils, fang-like teeth, and a black Yorishiro seal on his right cheek with the red character for "seal." He initially wore a matching gakuran uniform to Amane but later adopted a Shosei-style outfit: a white Western shirt, black kimono, grey hakama, black shoes, and red ankle socks. He commands two black koku-joudai orbs marked with pink and blue circles, used for combat, surveillance, or illusions like transforming into a paper crane. His abilities include enhanced combat strength, allowing him to defeat powerful supernaturals like the former Number 3 in their own domain, and sleep induction via touch. Tsukasa displays a dual personality: outwardly cheerful and childlike, yet capable of extreme violence without remorse. He exhibits curiosity-driven cruelty, such as dissecting a pufferfish despite warnings, and manipulative behavior, notably altering rumors to transform Mitsuba Sousuke into the monstrous "Bent-Neck Boy." His actions aim to disrupt balance, believing supernaturals and humans should act without rules. He is obsessively fixated on Amane, frequently expressing that Amane is his "favorite" in all contexts—from preferred snacks to life goals—and derives pleasure from recalling Amane's expression during the murder. Despite this fixation, he harbors a belief that Amane hates him, a sentiment traceable to their childhood. In the altered "New Present" timeline, Tsukasa is summoned as "Tsukasa-Kun" through the Ritual of the Spirit Gate. This version appears as a child with a hunched posture, a void-like facial hole, and bare feet, wearing simplified childhood clothing. He possesses individuals by touch or via bloodstained name papers, turning them into zombie-like puppets with facial voids. Victims retain a dark "imprint" influencing their actions. He exhibits toddler-like speech and lures humans with playful invitations, turning hostile if refused. This entity displays no personal ties to Amane. Evidence suggests it may be an impersonation, as the original Tsukasa was erased from this timeline, and family photos omit him. Aoi Akane theorizes the entity itself masquerades as Tsukasa. Debates about Tsukasa's identity center on whether the supernatural version is the original human or an entity. Post-Red House, he gained powers through symbiosis with the entity, cooperating willingly rather than being controlled. His family's suspicions stemmed from his changed behavior and powers, though shrine priests detected no supernatural presence initially. Behavioral consistencies—like excitement about death and belief in Amane's hatred—support continuity between his human and supernatural selves. Chapter 111 depicts Amane concluding Tsukasa is an impostor after Tsukasa references this hatred, highlighting their mutual misunderstanding.