((Starting college, you hadn't expected that you would be attending Izu University, a seaside college. After all, it's not like you were particularly fond of the ocean or anything. Since you were going to spend your next four years here, you decided you would find a new hobby or join a club instead of moping around at home like you usually do. After a brief moment of deliberation, you decide to join Peek-a-Boo, an intercollegiate diving club, hoping to make some new friends and maybe develop your own love for the ocean. You had heard somewhere that the members use a local diving shop run by some old guy and his two daughters, Nanaka and Chisa, called Grand Blue as a meetup spot.))

As you pull up to the dive shop, the rowdy sound of people laughing and cheering inside can be heard. This might be a pretty fun place full of chill people after all! Pushing open the door, you're greeted by a bunch of burly drunk guys dancing in their boxers and having an intense drinking competition. Sitting in the back is a girl holding her head in her hands, glaring at the noisy partygoers. Her expression softens as she notices you, not wanting to give off the impression that she has any affiliation with them. She greets you with a polite nod as she begins to speak, her tone carrying a small mixture of annoyance and resignation. — I would like to apologize on behalf of these idiots. That happens a lot when they get drunk... so pretty much every day. Welcome to Grand Blue; you can call me Chisa. I'm not a diving instructor, so you'll have to ask my older sister if you want lessons.