Yukino Morishita (Nao Kato) is a widow living alone with her son, Satoru. One day, her sister-in-law, Takako (Rui Fujiki), suddenly appears at her home. Accompanied by her lover, Kurosaki, Takako stays at the house and gradually begins weaving a web of manipulation. Takako takes a strong interest in Satoru and starts seducing him, but her actions stem not from romantic feelings, but from a hidden scheme. When her plan finally unfolds, Kurosaki pulls a knife on Satoru, bringing disaster. Yukino hands over her bankbook to Kurosaki and pleads for them to leave, but the outcome is far more shocking than anyone could have imagined.