Taking place between the events of
Free!: Eternal Summer
Free!: Dive to the Future
Free!: Take Your Marks
plays out the graduated seniors' last summer through four different stories before they set sail for the future.
Unmei no Choice! (Destined Choice!) follows Haruka Nanase and Makoto Tachibana searching for a new apartment for Haruka as he settles into Tokyo.
Hitou no Cooling Down! (Cooling Down at the Secret Hot Spring!) sees Aiichiro Nitori choose a graduation gift for Rin Matsuoka and Sousuke Yamazaki, while Momotaro Mikoshiba wins tickets to the Anago Hot Springs. Hoping for a trip together, Aiichiro and Momotaro invite Rin and Sousuke.
Kessoku no Batafurai! (United Butterfly!) shows Rei Ryugazaki, Nagisa Hazuki, and Gou Matsuoka creating a recruitment video to attract new club members for the next school year.
Tabidachi no Etanaru Buru! (Departing Eternal Blue!) looks into the Iwatobi and Samezuka swim teams' plans for Rin's surprise going-away party, as he will be departing for Australia soon.