One Piece: The Free Shinigami

(No female lead, no killing Luffy, and no joining the Straw Hats. At heart, this is just a story where the author makes up for a few personal regrets. If you're looking for nonstop slaughter, this isn't for you.)

A young man who inexplicably possesses the powers of both a Soul Reaper and a Hollow sets out to take these seas by storm. The Seven Warlords of the Sea, the Four Emperors, even the Celestial Dragons-all are nothing more than grass beneath his feet.

(New author here. My prose and plotting are gradually improving. If it's not to your taste, please don't flame me.)