Ogre Slayer Vol 1

From the VIZ Media edition

A gothic horror tale with elements of Japanese mythology and modern psychology, Ogre Slayer tells the story of a young man with a monstrous being living in his body. Armed with a legendary sword called the "ogre slayer", he searches the world for others like him, believing that their destruction will lead to the gift of a true human life for himself.

Source: Anime News Network Encyclopedia