Mujaki no Rakuen(4592)

Other Title(s)Paradise of Innocence
Genre(s)Comedy, Ecchi, Romance, School, Seinen
SynopsisShouta, a 25-year-old NEET, is mocked by his former female classmates who've all become successes, at their class reunion. A mysterious incident at the school pool throws him back in time and lets him deal with those same classmates back when they were fifth grade girls.