Rin Itoh, Seiichi's stepmother, becomes entwined in a clandestine sadomasochistic relationship with him, fracturing her marriage to his father and her bond with her daughter Kiriko from a previous union. Publicly, she cultivates a resolute, prideful facade, deflecting external scrutiny of her choices, while privately indulging submissive desires through her entanglement with Seiichi. This duality fuels escalating friction with Kiriko, who harbors her own burgeoning affection for Seiichi. Rin initially masks their rivalry as protective maternal instinct yet resorts to coercive measures to dominate her daughter.

Her dynamic with Seiichi serves as an outlet for repressed facets of her identity, starkly opposing her authoritative exterior. As familial tensions intensify, Rin’s actions deepen divides, particularly with Kiriko, now both a daughter and competitor for Seiichi’s attention. The psychological interplay between her concealed self and societal persona unravels, exposing the cascading repercussions of her duality on those entangled in her orbit.