Michiya, a young salaryman, is in a secret relationship with the admired student council president, Mafuyu. Their cousin Mana, who deeply admires Mafuyu, is outraged by the pairing and attempts to break them apart. However, after Mana catches them in an intimate moment, Michiya forces her to experience sexual pleasure to silence her and make her understand Mafuyu's feelings, leading to a complicated and secret arrangement between the three.
Michiya's relationship with the brilliant Mafuyu is challenged by his jealous cousin, Mana, who attempts to tear them apart. After a volatile confrontation leads to a forced encounter that unexpectedly awakens Mana's desires, the trio descends into a chaotic, dominant-submissive dynamic. While they find temporary harmony in a shared sexual encounter, Michiya's request for a new partner threatens to reignite the conflict.