Shouta Handa is a jobless twenty-five-year-old fed up with his dull life. At his class reunion, the girls he once sat beside have become successful, attractive women, and they know how little he has made of himself, so they mock him as a loser just as they did years ago. When he steps out for a smoke, he tumbles into the school pool, and a supernatural event sends him back in time. He surfaces in the same pool in the middle of swimming class, a grown man in a boy's body, surrounded by those same classmates as fifth-grade girls. The three-episode OVA mixes comedy, romance and ecchi as Shouta faces the girls who once looked down on him.