When Iori Kitahara heads off to college, he decides to live at his uncle's dive shop in Izu. Iori is looking forward to experiencing college life, but ends up running into a group of tough guys playing strip rock-paper-scissors. Iori gets dragged into the diving club's crazy shenanigans and ends up spending his first day in college wearing nothing but a pair of underwear.

Inori and Kohei get through their exams by cheating. Meanwhile, PaB throws a welcome party for Aina, their new member. Aina was looking forward to getting a new start to college life, but discovers that no one in the club is normal! Nevertheless, the club members are serious about diving and have the new members learn basic hand signals and dive in pairs. However, Iori gets paired up with Chisa.

For the last half of their trip, the Peek-A-Boo members arrive in Miyakojima. Everyone goes for a serious dive into the majestic sea with the exception of Iori, who couldn't obtain his license. Everything is magical with the stunning coral reef, colorful fishes and sea turtles, until the members engage in PaB-style Otori (a drinking custom of Miyakojima), which turns things into a living hell...