Idk. But maybe this person never had as much love as they ever wanted, so someone showing their undying love to them (physically, emotionally, and mentally) has entrapped them?
Probably understood that this is his best chance to get power over the king and he seems to have accepted the reality first but probably not in love regardless.
He had the idea to use him to his advantage since the king is obsessed with him and make him at least a little bit better Manz gonna do what ever Sam-myeong wants.
Where did this suddenly change of heart come from???