Rereading this, I now realise Yang Kai barely tried to fight the archer at all. So, naturally that would give the archer a helluva lot of leeway to act however they wanted to, as opposed to Yang Kai. I suppose Yang Kai being able to cure the ink corruption, he really really doesn't want to kill inked humans, whereas the inked humans will kill him in a heartbeat if given a chance.
Maybe he should deink some ink clan members just for laughs. Would that create an ink clan member enslaved to humans?