In elementary school, the four members of the swimming club won the championship in the swimming competition before graduation. After that, some of them graduated, some went abroad, and the four went their separate ways. As time passed, Nanase Haruka (voiced by Shimazaki Nobunaga) and her good friend Tachibana Makoto (voiced by Suzuki Tatsuhisa) who were studying at Iwatobi High School were promoted to the second year of high school. They reunited with one of the former members of the swimming club, Hazuki Nagisa (voiced by Daishinaga Tsubasa). The three recalled their elementary school days and agreed to go to the old swimming pool. In the abandoned swimming pool, they actually met Matsuoka Rin (voiced by Miyano Mamoru) who had returned home. Unexpectedly, Rin, the former comrade-in-arms, changed his temperament and challenged Haruka, but Haruka lost to him. Haruka, Makoto and Nagisa decided to set up a swimming club. After many efforts, they finally recruited a new member, Ryugasaki Rei (voiced by Hirakawa Daisuke). They aimed to win the county championship and conducted intensive training. On the other hand, the swimming club of Samebe Academy where Rin was was also preparing for the competition. They agreed to compete in the arena. The passionate and energetic swimming club begins a Free! story about friendship and youth this summer.