As Haruka Nanase and his friend Makoto enter Iwatobi Junior High School, they join the swim team and aim to compete in the medley relay with Asahi Shiina and Ikuya Kirishima. With diverse personalities and motivations, the four students struggle to work together, each carrying their own emotional baggage.

High Speed! Free! Starting Summer
A group of friends strive to become the best medley team, learning valuable lessons about collaboration, determination, and the power of close relationships along the way.