If I were Yohan, I'd tongue kiss hyunmook and make sure he gets more corrupted so he will go "yangyang" cutely every time I catch my breath. So yeah, he really needs to be sorry for turning back to normal.
If I were yangyang, I'll make sure to ruin hyunmook even further to keep him in his corrupted state so I can watch him make sheep noises and act all cute beside me.
If I were Yohan, I'd tongue kiss hyunmook and make sure he gets more corrupted so he will go "yangyang" cutely every time I catch my breath.
So yeah, he really needs to be sorry for turning back to normal.