After losing her husband, Miku Hasegawa chose to raise her son alone, supporting their life through work as an ear cleaning esthetician while struggling with daily emotional turmoil. One day, regular customer Takekawa proposes marriage, prompting Miku—worried about her reclusive son Kazuya—to visit a support center for shut-ins. Taking their advice, she sneaks into Kazuya's room, where she discovers a collection of mother-son incest porn videos. Realizing her son's true feelings, Miku succumbs to temptation and commits an irreversible act with him—just once. But this single decision spirals into a tragic chain of events from which there is no return.