Shouji is in love with his childhood friend, Medaka. When his mother told him that he has a fiancee, he ran away from home. Then his mother told him, "I don't care with whom, but you should marry after school graduation." Thus he started to live in Medaka's house in another city, and started to attend her school (originally an all-girls school).

After that, his fiancee, Toki, was also forced to go to this school. She forced him to help to establish and join the swimming club since he accidentally saw her panties. Medaka and her friend also joined the new club. Their exciting swimming club activity starts...