metraprix_12
of reading
1651
Read books
I don't think he can win much in that world that he can't get on hotd besides the fighting techniques that are not that useful for him if he plans to go to any other world with superpowers
one piece there are space and time powers, also a lot of different martial arts, sword techniques and you have haki too plus a lot of genius scientists and medics
I like more One Piece, but as others said JJK should be an easier way to be OP, then I would go to One Piece for the diversity of powers and Danmachi just to get some god ADN