[No System + Not a power fantasy + Not invincible + Character growth + No harem + A slightly slow start + Momonosuke must die]
The Sun God isn't Nika, but the Flame Emperor!
After the protagonist, Bai Xi, a hardcore One Piece fan, transmigrates into Ace's body in the world of pirates, he unexpectedly discovers that this world is completely different from the one he imagined.
My name is Luffy. I'm going to become King of the Marines.
My name is Kaido. I will protect justice.
My name is Sakazuki. I'll be damned if I don't claim that accursed One Piece before Kuzan and Borsalino!!!
Bai Xi: Since I'm here, I'll bring true justice to the whole world!!!
(This story only swaps the roles of the Marines and pirates. In the original story, the Shichibukai are pirates with official appointments, and theoretically they're on the Marines' side. So in this story, I'm counting them as pirates. I hope you understand, dear readers. Thank you ((*^∀^*)) )