Fumie, happily married with a son who diligently studies, lives a peaceful life with her family. She often sees her son studying hard alongside his close friend Takashi, and Fumie warmly watches over them. However, one day when her son comes home late, Takashi remains alone at the house. While bringing him a drink, Fumie is suddenly shocked when Takashi abruptly changes demeanor and makes a move on her. Shaken and distressed, she chooses to bury the incident. From then on, Takashi begins visiting more frequently, and eventually starts showing up even when her son is not home. A series of events unfolds that threatens the happiness of her family.