High☆Speed!

A sixth-grade student named Haruka enjoys swimming and the connection he feels with the water. He regularly trains at a local swim club alongside his childhood friend Makoto and Nagisa, who is a year younger. As winter approaches and graduation nears, a new student named Rin joins their school from a different swim club. Haruka's friendship with Makoto and Nagisa deepens through their shared swimming experiences, and he also grows close to Rin. Inspired by Rin's enthusiasm for the medley relay, the group considers forming a team to compete in a tournament.