Makoto reveals to Nagisa that he has great problems with Haruka stripping all the time. As he explains , he went out shopping with Haru the day before and Haru, upon spotting a large fish tank, left Makoto behind to strip and try to get inside. When stopped, Haru always becomes irritated. To discover why Haru behaves this way, Nagisa decides that they should conduct an experiment.

During lunch time Nagisa starts the “Ideas on how to bring in more members to the swim club” 'conference' atop the Iwatobi High School and suggests that new members should receive an Iwatobi-chan changed from the 'Novel version' to 'Swimsuit version', but Makoto doesn't think that that's a good idea.

Beginning on Monday, Nitori announces he's completed writing and arranging his schedule for the next week just before midterms take place. As he shows off his work to Rin who is reading quietly in his bed, Rin takes note of how disorganized Nitori's desk is. Nitori thanks Rin for his concern, but in the end keeps his desk as it is as he claims to know where all his books and school supplies are without fail.

The short begins with Rei, dressed in the penguin Speedo Nagisa lent him, getting ready to jump from his diving block at the edge of the pool on the Iwatobi High School campus. Just as he dives, however, he suddenly wakes up during class and ends up rattling his desk which surprises and silences the entire classroom. Surprisingly, Rei had been daydreaming all along. Just behind him, Nagisa bursts out laughing to which Rei frantically yells at him to stop.

Rei is worried as he does not have a swimming suit except for the one he had when he was in elementary school. Just as he was worrying, Nagisa came in showing him a bunch of swimming suits and asking him to choose one as he had to take responsibility due to what he said before Rei joined the club. However, Rei cannot make up his mind, thus, Nagisa calls Makoto and Haruka to give advice. In the end, Rei chooses a speedo due to what Makoto had said.

Rin observes the members of the Iwatobi Swim Club doing handstands in the water.

Rin pointed out that he had never heard Haru laugh. Makoto states that he had during elemetary school but also said it was a scary laugh (sleep talk). Rin suddenly grabs Haru and tells the rest to tickle him. Just as they do it, Haru bursts out laughing. Everyone gets shocked and then hugs Haru.

Haruka and the others go to Samezuka Academy's Culture Festival, where Rin and the rest of the swimming club are hosting a maid café. Both the Itwatobi and Samezuka teams decide to participate in a watergun survival game across the campus, with Haruka, Sousuke, Nagisa, and Momotarou on one team and Rin, Makoto, Rei, and Aiichirou on the other. After several mishaps and plans gone astray, the match boils down to a standoff between Haruka and Rin, which Rin wins due to Haruka's affinity for water. At the end of the day, the eight of them take the time to get to know each other better.