Rin reminisces with Sousuke, his classmate prior to transferring to Iwatobi during elementary school, who decided to spend his last year of high school in his hometown before swimming professionally. Meanwhile, Goro plans to put on a swimming festival for the Iwatobi Swimming Club for children, asking Haruka and the others to spread word and come up with a main event, with Haruka suggesting a relay event. With Rin asked to assemble a team of his own to swim against them, Sousuke asks to join on the condition he run in the freestyle leg. On the day of the event, one of Rin's team members is forced to drop out, but they manage to find the former team captain's brother, Momotarou Mikoshiba, to fill in for him. Prior to the relay, Sousuke confronts Haruka, telling him not to get in Rin's way. As the relay gets underway, both teams show strong form with Haruka's team narrowly managing to win. Afterwards, Rin invites Momotarou to join his swim club whilst Haruka becomes cautious of Sousuke's attitude towards him.