Oh so when he stopped putting himself in harm and started contributing something to the escape, now he is changed and cannot be trusted. Just no.
If it at least was framed as the detective convincing her he is evil, or him getting his key did something to him, but it doesn't seem so.
So I guess the implication is supposed to be he always had this power, but they were dormant for some reason and Ruka healing him didn't give him the power, but activate it; we aren't going into a twist that he is the bad guy that set everything up are we?