One Piece 18

First island on the trip with the new ship is a little plateau with another little plateau on it, guarded by someone who calls himself god, but turns out to be just a man in a box.

It also turns out that the man in the box has been shipwrecked on this island for 20 long years.

His name is Gaimon, and he came there looking for a treasure together with his crew, but when he had climbed onto a plateau (on which he saw five treasure chests btw) he lost grip and fell into an empty treasure chest below. Even worse, he was stuck, and the boat was leaving.

So since then he was stuck on the island, and stuck in a box, guarding a treasure he can't reach (since he's stuck in the box). Luffy checks out the plateau and it turns out all chests are empty. Gaimon takes it pretty well, he says he feels free for the first time since he came to the island.

They ask him to join them but he says he'd rather stay there with all his animal friends. So that's the way this story ends. Sail on!