Shōta Handa is a 25-year-old NEET who suffers crushing social humiliation when successful former female classmates mock his unfulfilling life at a reunion. This triggers a supernatural event where he falls into his old elementary school's swimming pool, transporting him back roughly 15 years.

Physically regressed to his 10-year-old self but retaining adult memories and psychological maturity, Shōta finds himself in a fifth-grade classroom surrounded by the younger versions of the women who ridiculed him. His adult consciousness views these prepubescent girls through a lens of sexual curiosity and perceived opportunity, starkly contrasting with their actual age.

Shōta consistently wields his advanced age and future knowledge to manipulate social dynamics involving his female classmates. He orchestrates incidents like coercing boys to spray girls with spoiled milk to force clothing removal. He devises scenarios for physical contact, feigning help during bug-collecting to extensively touch a girl or exploiting gymnastics training to inflict painful splits mimicking sexual positions. These actions consistently induce his sexual arousal, often resulting in visible ejaculation while he maintains a child's exterior.

Shōta exhibits no substantive moral development or remorse. His adult mind fixates solely on exploiting the time displacement for sexual gratification, not personal growth or rectifying future failures. The narrative concludes without his return to the original timeline or meaningful alteration of his adult path, leaving his predatory behavior unresolved. A sequel manga, *Paradise of Innocence Parallel*, exists, though Shōta's presence or role within it is unspecified.