Rebirth in One Piece as Deputy Captain - Chapter 587

King Grey has unrivaled strength, wealth, and prestige in a world governed by martial ability. However, solitude lingers closely behind those with great power. Beneath the glamorous exterior of a powerful king lurks the shell of man, devoid of purpose and will. 

Reincarnated into a new world filled with magic and monsters, the king has a second chance to relive his life. Correcting the mistakes of his past will not be his only challenge, however. Underneath the peace and prosperity of the new world is an undercurrent threatening to destroy everything he has worked for, questioning his role and reason for being born again. 

Reiji Saeki, who lives in the north eastern countryside town, lost his life in an accident during summer vacation. ……But before he knew it, a mysterious ball of light hovered in front of his eyes in a world of whiteness. That ball of light was a magician from a parallel world, and is looking for a person qualified to inherit the magic they had created to prevent it from being lost. Reiji, who rode on that suggestion, now lives in the parallel world Elgin, with a new body and powerful magical power.

This novel is also known as Don't Mess with the Dark Princess

When trash becomes a genius—one word: Fierce! Two words: Two-faced! Three words: Too heaven defying!

She is the foremost and outstanding armament refining master. Passing through a dynasty, and became a publicly humiliated and bullied Third Young Miss. Ancient beasts, too outrageous? Obediently become a docile pet, or I’ll make you into soup!

Ninth rank talent, rare talent in a thousand years? She was born with a godly constitution, crushing all geniuses!

Peak level Profound Grade Armament, beyond priceless? Sorry to embarrass, but the bowl she uses to feed the cat is already at the God Grade….. she possessed a pair of eyes that could see through everything, yet she couldn’t see through—him!

Merely exposing his demonic smile, Prince Mou lightly loosened his belt: “Can’t see through? Do not fret, you can slowly view when you return to the room. I’ll allow you to scrupulously inspect from head to toe.”

- Description from Novelupdates