I've been thinking about it actually. But a bit differently from you. I'm sure though, he's definitely not a normal person. I thought about it and I think he's the Salami guy XD! I mean, they just happened to casually mention the slave, and then Salami comes into the picture... typical foreshadowing. Well, if I'm wrong, I'm wrong HAHAHAHAHAHAHAHA
Actually, before I knew about Salami, I was thinking a different conspiracy. I thought he was a bad guy, cause it's weird to stay as a slave when you were already given freedom. So I thought he stayed to, you know, gather intel from the inside. But still, not sure. He can go both ways either way. He can be a bad guy or a good guy. Not gonna change the fact that he's still pretty cute. XD!
Am I the only one who been thinking the silver haired ex slave could be the demon king himself? Just me? K (=・ω・=)