The mundane daily life of an ordinary family of three is shaken by the forbidden emotion of familial desire. Winter beauty, unsatisfied with her husband's sex life despite his undiminished vigor, finds herself overwhelmed one Sunday afternoon when her son, wearing only his underwear, goes to get a drink. Unable to suppress her hidden feelings, she becomes aroused. Unable to endure it any longer, she indulges in masturbation imagining her son. As these days continue, her husband suddenly leaves on a business trip, leaving her alone at home with her son. Then, mother Fuyumi's uncontrollable emotions explode—her longing for her son finally manifests into reality.