Iori Kitahara heads to the shop Grand Blue to meet with his extended family and start his new college life. However, he is shocked to discover the shop overtaken by several rowdy, drunken, naked men. As Iori runs away, two of the men from the diving club chase after him, eventually catching him and dragging him back to the shop. While trying to find someone to take the scene seriously, Iori gets swept up in the antics of the club, getting drunk and stripped of all clothing except his boxers...