Four years ago, Miki and her husband remarried, each bringing a child from a previous relationship. Initially uncertain, Miki soon found comfort in the fact that her husband's son was kind and had developed a close bond with her own son, who looked up to him like a real brother. Miki's son, having never learned how to masturbate on his own since childhood, had always relied on his mother to relieve him. One day, after throwing a tantrum, he demanded she pleasure him again. At that very moment, his older stepbrother returned home and secretly crept into the room, watching Miki intently. That night, as Miki stepped out of the bath, the boy suddenly approached her and whispered, "I saw what you did..." From then on, he began aggressively pursuing her. Torn and confused, Miki finds herself drawn into an increasingly intense and forbidden relationship, leaving readers captivated by the unfolding drama of desire, guilt, and taboo.