Fuyuki Yamamoto, a 34-year-old manager of the idol group Mystery Kiss, combines a tall, striking physique with a reputation for earnestness. His unwavering dedication to the group’s success pushes him into ethically murky territory, forging alliances with yakuza operatives to secure vital evidence tied to a missing girl’s disappearance. He becomes complicit in concealing the murder of Yuki Mitsuya, a founding member, aiding in the clandestine disposal of her remains.

Driven by loyalty, Yamamoto resorts to drastic acts to shield Mystery Kiss, nearly strangling the protagonist during a confrontation that risks exposing his crimes—an intervention thwarting his desperate bid for secrecy. Though entangled in blackmail, evidence tampering, and violence, his choices stem from a warped sense of duty to preserve the group’s image and longevity.

A key twist reveals his perceived animalistic features originate not from reality but from the protagonist’s visual agnosia—a psychological distortion rooted in childhood trauma. His true human form contrasts with the protagonist’s fractured perception.

Yamamoto’s underworld connections include subordination to yakuza figure Yano, implicating him in broader criminal networks. While instrumental in suppressing scandals and manipulating events, he remains a subordinate antagonist, overshadowed by more powerful conspirators orchestrating the central mystery.