One day, Jun visits his friend Shota's house and accidentally witnesses Shota's mother, Ria, masturbating while on the phone with her secret lover. Jun has long harbored feelings for Ria, and though shocked, his youthful desire overpowers him as he sees her lewd act. He threatens to expose her affair to Shota unless she complies. Desperate to keep her son in the dark, Ria proposes a deal with Jun—but gravely underestimates the depth of his lust. As a result, Ria's life spirals into an endless frenzy of depravity.