Kurō Sakuragawa, a young man with supernatural powers acquired through childhood experiments, ingested flesh from two yōkai—the Kudan and Ningyo—under his grandmother’s guidance. These trials, part of the Sakuragawa family’s generations-long pursuit to create an immortal future-seer, claimed most participants’ lives. Only Kurō and his cousin Rikka survived, emerging with immortality and precognition. Enduring repeated trauma to test his regeneration, Kurō developed emotional detachment and a muted pain response.

Physically, he stands tall with light skin, black hair, and piercing yellow eyes. While appearing ordinary to humans, yōkai perceive him as a grotesque hybrid of human and yōkai. His body secretes a toxin fatal to supernatural beings, evidenced when a yōkai perished after biting him. Kurō’s immortality enables rapid healing from catastrophic injuries—limb loss, head trauma—via regrowth or damage reversal. His precognition activates during near-death crises, allowing him to sift through possible futures to select viable outcomes, constrained by logical plausibility.

Shaped by childhood trauma, Kurō exhibits stoicism and avoids confrontation, initially maintaining emotional distance in relationships. His first attachment, cousin Rikka, influenced subsequent romantic choices. After a years-long relationship with Saki Yumihara ended when she witnessed his abilities and fled, Kotoko Iwanaga pursued him. Their bond, outwardly platonic, gradually revealed Kurō’s protective instincts and buried affection. He eventually acknowledges deep romantic feelings, openly relying on Kotoko and shielding her from yōkai exploitation.

As Kotoko’s partner, Kurō tackles physical threats while she strategizes, forging a brains-and-brawn duo. Together, they confront supernatural crises like the Steel Lady Nanase incident and Yuki-Onna murders. His loyalty to Kotoko intensifies, though tensions simmer between his immortal nature and her role as human-yōkai mediator. Rikka’s reappearance strains their relationship, hinting at future clashes should Kurō’s existence destabilize the supernatural order.

Kurō’s growth includes subtle emotional shifts: visiting hospitalized Rikka, balancing Kotoko’s ideals with pragmatic governance, and prioritizing her safety. Despite a reserved exterior, he increasingly voices concern for her well-being. His immortality’s psychological impact and erosion of humanity remain central, underscoring narratives of sacrifice and connection amidst eternal life.