Makoto and Nagisa watch with their breaths held as Haruka and Rin engage in an intense race. However, they notice that Rin appears to be have changed. At the same time, Nagisa prepares to start up a swim club with help from Rin's sister Gou.

The Iwatobi Swim Club must win to advance to nationals. As the tournament draws near, the members get nervous. Meanwhile, Rin grows increasingly irritated. As it comes time for the medley relay, each member must find their own answer as they step up to the start line

After hearing about what happened in the past, Rei goes to Samezuka Academy to ask Rin what he wants. The night before Iwatobi and Samezuka leave for regionals, Rin calls Rei to explain how he feels about the relay. And then, Samezuka announces its lineup for the relay.

Coach Sasabe begins training the Iwatobi Swim Club for the upcoming tournament. Meanwhile, Rei is unhappy about the fact that he's the only one who doesn't know about what happened with Rin in the past. After Rin expresses his frustration, Haruka decides to tell him about what happened when they were in grade school.

After spending their first year of high school in peace and quiet, Haruka and Makoto run into Nagisa, a new student who was a member at a swimming club with them when they were kids. That swimming club is being torn down, so the three of them sneak in to dig up a time capsule that they buried in the back, which is when they are reunited with Rin, the fourth member of their group who left to study abroad.

Okabe's stubbornness causes fists to fly and tears to be shed as the deadline for using the time machine swiftly approaches.

Shirou and Sakura are asked to help clean up Rin’s house which is full of magical devices and Spell Tomes. As the three of them are busy tidying up the Tohsaka residence, lunchtime approaches, and it is Rin and Sakura’s turn to cook today’s lunch.

"I want you to find out who killed my husband." Three years ago, someone shot Count Maupassant to death. His widow, Isabelle, summons Lupin to her home, with her requesting he investigate her case. There are three suspects, and then... more murders. Along with the old castle being locked down. "I'm Jim Barnett. A detective, hired by the countess." Get a good look at the once time appearence of Detective Lupin!

apa is visited by two of his underclassmen. The first one can’t seem to stop paying for microtransactions and the second needs ideas for a new game featuring anthropomorphic characters.

Ains decides to go and see the Giant of the East and Demon Snake of the West himself. If they are similar to Hamusuke, they may have some worth as experimental subjects. They may also be useful in testing Lupisregina's capabilities with the village.

The girls goes to the beach!

Asta and the other Black Bulls are split up throughout the Underwater Temple due to Gifso’s magic. They are forced to go head-to-head with the temple mages in a battle royale.

The Build Divers members are wholeheartedly enjoying their new Force Nest, an environment so lavish that it rivals those of the most famous forces. Yukki voices his admiration for Riku, who has greatly improved as a Diver. But meanwhile, a new wish has formed within Yukki's heart.