Yuka is a mother who has raised her son, Kosuke, on her own. As she goes through daily life, she notices her son's growth, but also feels hidden guilt and uncontrollable desire as she sees the resemblance between him and her late husband. Meanwhile, Kosuke harbors deep affection for his mother, keeping it concealed while living his everyday life. However, on the night before his wedding, he discovers Yuka masturbating and, overcome by impulse, says, "Since this is the last night we'll spend together as mother and son..." as he moves close to her. There, he gives in to his own desires, and their relationship deepens further. A forbidden love begins to bloom, stirring a whirlwind of new emotions.