Kyon becomes a servant for a half-zero royal blood. He goes his way to disobey his master because of his desire to get to know him, the savior he knew when he was young, when a Zero killed his family. Lucaon, a hunter who had to kill his father who was poisoned and turned into a zero, grew to be hateful and distrustful of servants. Thus, he projected his hate on Kyon, the nosy servant who remains by his side even if he is rape and abused. The two ends up deeply in love amidst secrets unearthing.
Sihan and Karis are master and servant yet they are lovers, too. Sihan is overprotective, but Karis is stubbornly reiterating that he is strong enough to do his job as a servant and hunter. These two are the wholesome couples.
Ryan is Lucaon and Sihan's guardian. The man who basically watched over Lucaon's family since his parents. He also saved Sihan from captivity and turned him into a royal blood. He also took in a servant, Christoff who ends up being the root of all suffering, even his death. Nonetheless, Christoff was a pawn, brainwashed and ordered. But Christoff fell in love with Ryan and before he knew that he caused Ryan's corruption and ultimate death, Ryan had his memory wiped from Christoff's mind, along the other traces he left.
Cecilia, a familt friend of sorts, comes in later to tie the loose ends of Ryan's death and would take over as the guardian of Sihan and Lucaon.
Anyway, it had a plot regarding the family's poisoning incident and also the mission to make an antidote. Midway through, it became character-oriented instead. The truth came up and it ends there, antidote is not taken care of anymore.
Royal Servant