Since her husband's death, Emi has raised her son Hikaru on her own. But now that Hikaru is finally becoming an adult, Emi feels a tinge of anxiety along with her joy. While she has done her best as a mother, she has forgotten that she is a woman for the past few years... Since realizing this, Emi has been experiencing a sudden thirst for physical satisfaction and has been comforting herself almost every day. However, her solitary, obsessive masturbation in a dimly lit room drives Hikaru, who cares for his mother, to unexpected actions.