The obligatory swimsuit episode pops up when Yuuji tries to spend the night at Akihisa's house only to find that he has no hot water after getting sprayed by a freezing shower. After arguing about Akihisa not paying the gas bill, the two of them try to sneak into the school's pool. However, they are caught by the teacher who cuts a deal with them: they can use the pool on the weekend, but they'll have to clean it. So they invite all their friends to show up, including most of the main cast.
After coming out with their swimsuits by the pool, more crazy antics pop up. Shouko repeatedly pokes Yuuji in the eyes, the men try to avoid having to eat Mizuki's cooking, and everyone is gay for Hideyoshi (who apparently now has his own changing room). After a massive nosebleed explosion in the pool (caused by Hideyoshi accidentally losing his top), the cast decides to head to a nearby hot spring and finish their day there.
At the hot spring, Akihisa makes use of his special bracelet to summon his Being and try to take pictures of the girls, but the girls take advantage of the situation and summon all their Beings at once to crush Akihisa's, forcing his HP down to 0 before he can make it take a picture. The teacher from before, who happened to be hiding in a nearby bath, drags Akihisa back to school for supplementary lessons.