After the match, Haruka Nanase and the others are once again reprimanded for trespassing on Samezuka Academy grounds. Makoto Tachibana and Nagisa Hazuki run into Gou Matsuoka and they all agree that Rin Matsuoka's attitude had dramatically changed in the past few years, simultaneously learning that Gou had been the one who sent him to the Iwatobi Swimming Club while Nagisa suggests that they form a school swimming club.
After getting Haruka on board, Makoto and Nagisa propose the idea to their homeroom teacher, Miho Amakata, who agrees after they give her a little prompt. Finally, the club is accepted by the faculty on the condition that they find one more member and restore the school's swimming pool themselves. Nagisa begins the task of finding a fourth club member, which proves more demanding than initially thought.
While continuing the restoration, Gou, who is still confused about Rin's behavior, asks Makoto about the match race and learns that Haruka threw the match. This angers Rin who wants to win against Haruka swimming at his best. Believing that they can revert Rin to his old self, Gou volunteers to join the new swim club as their manager. Later, Makoto pays a final visit to the Iwatobi Swimming Club and runs into their old mentor, Coach Goro Sasabe.
Sasabe reveals that Haruka and Rin had a race when they were still at Iwatobi Junior High School and the latter made a rare return to Japan. Haruka easily won. Rin was exceptionally disappointed that his hard work was for nothing and said he was quitting competitive swimming, thus causing Haru to do the same out of guilt. Upon learning this, Makoto calls Rin to inform them of their new swim club plans while Rin decides to join the Samezuka Swimming Club out of his grudge against Haruka. Finally, Miho and the group officially re-establish the Iwatobi High School Swim Club and Haruka can't help but christen the pool with its first swim, much to his friends' dismay.