Azusa, a devoted mother who has lovingly raised her son, takes genuine joy in his growth. However, as he enters puberty, he gradually becomes withdrawn and distant, no longer relying on his mother's care. Though Azusa deeply loves him and tries every way to nurture him, she grows fearful of his intense, piercing gaze. One night, she discovers him stealing her underwear while she bathes and masturbating with them. Tormented by this discovery, Azusa seeks advice from her son's homeroom teacher—but this is only the beginning of an intense, forbidden descent into desire and taboo.