The Eclipse Demon (Demon Slayer x Male Upper Moon Zero Demon Reader)

There were stories of a demon stronger than even Muzan himself, a demon that had combined Sun Breathing and Moon Breathing, to create a Breathing Form that was deemed unbeatable, and this form was called Eclipse Breathing. He was called Upper Moon Zero and his name was Y/n and he also has a girlfriend as well, which happens to be Upper Moon One, Kokushiba. Y/n was born with the demon slayer mark same a Yoriichi, but instead of having a happy life, Y/n was mistreated because people thought his mark was a sign of the devil and evil. They called him a 'demon' but soon he would become the strongest demon in existence.