This is worse. This is so, so much worse. This is the answer to most of Ryo's questions, in perfect, horrifying clarity. Evidently his world had tested it at some point, locking Thanatos up- in a box- when he was small-

And as if that's not enough, Thanatos is blaming himself for his friend being in pain-

He's out of his seat and around the table before he knows it. Persephone may not be able to hug Thanatos, but Ryo has made no such promise. He takes a seat next to Thanatos and wraps his arms around him, not too tightly but enough to get through. "This isn't your fault," he says, as firmly as he can manage. "None of this is your fault." That is the important part; the details can wait.