[Crossover] A Survival Journey Starting on a Raft

The vacation is too long, and there's nothing to do. A lazy person picks up a tablet and starts tapping away.

A coming-of-age story, no CP. There'll be brotherly affection in the socialist sense.

The worlds aren't set: probably One Piece, Demon Slayer, Hunter x Hunter, JoJo, and Harry Potter.

I recently found the Zoo Rules horror stories really interesting, so I might add that too, depending on how things go.

Basically, it's a story about surviving, fighting monsters, leveling up, and growing in various worlds. A casual, sarcastic tone. Updates whenever.

Theme: What theme could there possibly be?