Claudia's neck is his collar. She was once a knight because she was destroyed by the demons in her country and her status was dropped to the guy ○. And this collar is not just a proof of the guy ○. It was a slave collar that could not go against the owner's orders. Claudia is not allowed to defy the demons who destroyed the country. Seeing Claudia, who becomes a puppet of the demons and does evil things, Hein can be released from her slave collar in some way.