Seth is a horned orphan of the "Infected" people, he lives with his adoptive mother Alma. He wishes to fight the Nemesis and his recklessness gets him into trouble. It isn't until he learns of the existence of "Radiant," the being of the Nemesis monsters he wishes to fight and destroy. He attends the Artemis Institute to get himself closer to defeating the Radiant.

Spoiler

He's the brother of Piodon and Diabal