(Voiced by Hikari Hazuki ): The protagonist who suffers from unrequited love for Rio.

The series features a small core cast that drives the emotional and sexual tension:

While Rio admires Kaito for the strength and bravery he displayed in their youth, Kaito has since changed into a more manipulative and darker individual—a transformation that Rio refuses to acknowledge. The narrative follows the psychological and physical entanglements between these characters as Haruta's secret affections collide with the reality of Rio and Kaito's relationship.