A high school teacher who continues private lessons at home, mother Yuriko has fallen into a forbidden relationship with her student. Upon discovering this, her stepson Hiroyuki is consumed by intense jealousy, forgetting all familial bonds as he assaults her. However, faced with Yuriko's unexpectedly blatant and lewd reactions, her virtuous image shatters completely, driving Hiroyuki to adopt a sadistic dominance over her. Meanwhile, Yuriko discovers her own masochistic desires, enduring her son's abuse while gradually succumbing to pleasure. Her pride as an educator vanishes entirely, revealing herself as nothing more than her son's sex slave.