Four new friends join the swim team and work to be the best medley team.

Haruka Nanase feels something special when he touches water and when he moves on to Iwatobi Junior High School with his friend Makoto and start a new life they both enter the swim team, and plan to compete in the medley relay together with Asahi Shiina and Ikuya Kirishima. All four students have different objectives and ways of thinking, and different baggage they're carrying, and so their practice for the relay hasn't been going well. What is required to make a team? What does Haruka, whose heart is trapped in the medley relay of the past, think during this new event?