Well yes, it has to be something along those lines.
Muzaka looks like he is sort of..programmed to fight Rai and he does seem to try to resist it. So maybe the 4 traitors ( I suppose there won't be any more traitor clan leaders ) with the cooperation of the current werewolf lord managed to mind control Muzaka and make him "betray" the werewolves and maybe attack people or something. Then Rai was informed and he was told that Muzaka just lost it so he had to do something about it as the noblesse. Then Muzaka attacked Rai and they fought and they both ended up sleeping for 820 years.
The strangest thing is why the hell was the cascet found in the bottom of the ocean?
It would be nice if the werewolves have some healing abilities. Or lets say if you drink their blood you heal yourself or whatever. That would help Rai in case Muzaka changes sides (which I bet will happen).
Muzaka doesn't seem like a bad guy, and like I said before he seems to be under control and under agony. He was Rai's one true friend. One does not simply become Rai's one true friend if he isn't noble enough.
He also seems like a badass, Muzaka ftw!