Eren Arkus, who can understand the language of monsters, used her ability to work at the Tamer Guild. However, he was persecuted by the people because he had black hair like the demon lord who was once the enemy of humans, and because he could understand the language of demons. The guild master, who considered Eren a heretic, unjustly banished him. Just when he loses everything and is on the verge of death, his bonds with the monsters awaken a new power in Eren!