Free! Timeless Medley

In middle school, Haruka Nanase decides to quit the swim team after a falling out with his rival Rin Matsuoka, causing Ikuya Kirishima to resent him. The swim team disbands afterwards, as Asahi Shiina moves away and Ikuya studies abroad. In present time, Haruka prepares for the tournaments with his teammates Makoto Tachibana, Nagisa Hazuki, and Rei Ryugazaki, while Rin, who has since reconciled with him, does the same. Though Haruka is in his final year of high school, he has not yet decided on what he wants to do after graduating, even after being scouted by a college during the prefectural tournaments. Meanwhile, Makoto becomes inspired to become a swim coach after helping Kisumi Shigino's little brother, Hayato, learn how to swim.

During the regionals, Haruka is overwhelmed from the pressure of performing in front of the scouts and stops in the middle of his individual event, angering Rin. When confronted, he yells at Rin about not having a dream and being told how he should swim, which concerns his friends. Makoto attempts to reason with Haruka, but they end up in a heated argument, in which he confesses that he has decided to attend university in Tokyo. Haruka feels even more lost and with prompting from Makoto, Rin takes Haruka to Australia. The trip inspires Haruka to swim professionally and upon returning to Japan, he makes amends with his team. With the bonds he has made with his friends, Haruka and his team place 6th overall in the nationals.

In a post-credits scene, during the nationals, Sosuke Yamazaki gets lost, only to end up watching the individual medleys, where Ikuya from Shionezaki High School overtakes everyone. After the tournament, Ikuya discusses his condition with his older brother, Natsuya Kirishima.

Sosuke Yamazaki, Rin's best friend from childhood, transfers into his class at Samezuka Academy. Rin and Sosuke had promised each other as children to continue their swim careers together, but unbeknownst to Rin, Sosuke has incurred a serious shoulder injury from overuse, yet continues to swim as they prepare for upcoming tournaments. While Rin is serious about swimming, Sosuke struggles to find a reason to continue, further straining their friendship.

At the regional tournament, Rin finally learns about Sosuke's injury. Sosuke, now cherishing the bonds he has forged with the swim team, is determined to participate in the team medley one last time. The team places second in the race, thus qualifying for nationals, and Sosuke decides to get medical treatment for his injury. Despite dropping out of the nationals, he offers to help Aiichiro Nitori and Momotaro Mikoshiba prepare.

In a post-credits scene, Sosuke warns Rin about Ikuya, whose freestyle resembles Haruka's in both form and speed. Meanwhile, Ikuya refuses to attend the nationals' awards ceremony to call Natsuya. Gou becomes determined to recruit new members for the next school year. Aiichiro, Momotaro, Nagisa, and Rei reaffirm their rivalry and plan a joint practice together. While Asahi exchanges farewells with his swim team at Kazami High School, he receives a text message from Kisumi. Haruka and Makoto arrive in Tokyo.