One Piece: I Join the Paramount War with a Proficiency Panel

Luo En transmigrates into the world of One Piece and gains a proficiency panel.

As long as he practices a skill diligently, he can raise his proficiency without limit.

To keep laying low and grinding proficiency, he decides to save Whitebeard during the Paramount War six days from now.

By tugging on the threads of fate, he saves Ace, but the price is the lives of Blackbeard's entire crew.

To get more time to grow before the final battle, he also kills Momonosuke and Kin'emon with his blade.

Thanks to his butterfly effect, Buggy even becomes the Pirate King, while Luffy cries himself unconscious in the bathroom.