In One Piece, I Join the Straw Hats with Advanced Knowledge

[Following the ship + Devil Fruit + weak early stage + doesn’t know the plot + basically follows the original story + light mockery + no female lead]

Starts out doing odd jobs, then follows the hot-blooded idiot protagonist on a voyage to gather companions, but it seems everyone has at least a little something wrong with them.

In the early stage, when facing enemies, he basically crushes everything from the front and accumulates experience from behind the group, but later on why does it keep turning into life-or-death situations?

...

Two years later, since you people won’t talk science, I’ll show you what magical science really looks like.

[The later part does not detail the original story very much. Readers need some familiarity with the source work, but anyone who reads One Piece fan fiction should be fine.]