ok I'm a little confused. Anton got engaged or married but he locked up arwin?

because he's afraid that someone might steal arwin from him, but locking arwin up is a good decision for both of them until the situation get calm

I think arwin wantedly locked himself up, in a way he blames himself for what happened to the arnaults and wanted to relive anton's worries by locking himself up in the room so that anton can have him all to himself. From what I understood it was his way of punishing himself....