Lee woyeon Doesn't know any better so he just follows his instincts like animals, because he can't feel pain or any other emotions, he even tried to control it, but Inseo knows what he is doing is wrong but he does it to take revenge. His pain has nothing to do with Lee woyeon because regardless of what he is thinking he hasn't been anything but nice to Inseo, so his pain comes from his own emotional conflicts and guilt.