A boy who is a member of the swimming club and is always fighting with his childhood friend, the captain, has a very tsundere personality. They used to bathe together when they were little but as they grew older and became sexually aware, they were shy and would just joke around about sexual matters. However, they both became conscious of each other's genitals through the fabric of their swimsuits during practice, and their interest in sex only grew. After one of their usual fights, they ended up having their first experience together in the shower room, still wearing their swimsuits.