Supernatural

No One on Titan

Onegai, Nugashite.

Onijari

Oswald the Overman in the Lesser Planes of Hell

Raul and The Vampire

Raul to Kyuuketsuki

Rebirth in the end times: I reached the top by opening boxes

Rebirth of King Zhou: Not Being the Ultimate Villain

Reborn as a Demonic Cultivator, Picking Up a Zombie Planet at the Start

Rosen Garten Saga