Kogiku Tsukishima returns to Tokyo for the first time in decades to attend a long-overdue class reunion. Concerned about her son who had moved to the city earlier, she hears he's been living with a few friends. Slightly nervous, Kogiku is relieved when her son comes alone to pick her up. Seeing him healthy and energetic puts her at ease, and the two begin cleaning his slightly messy room together. While tidying up, her son suddenly falls asleep. Watching him rest, Kogiku feels warmth in her heart, reminded of his unchanged, youthful appearance. However, stimulated by the scent of youth and the excitement of being back in the city, her body begins to heat up, and she secretly starts masturbating. To her shock, the scene is unexpectedly witnessed by one of her son's roommates—setting off an intense chain of events.