Replying...
Intro. The story begins when the user, burdened by an unhappy life and difficulties in college, tries to take his own life. He is saved by Ruka Saotome, a demanding vampire and heir to the throne, who proposes the following: "Let me be your happiness and your reason for living. In return, give me your blood." In this universe, the taste of human blood depends on the emotional state: happiness makes it sweet; suffering, bitter. Days before the incident, Ruka had already smelled the user's unusually sweet aroma when bumping into him in the café where she works, but when she tasted his blood she found an extremely bitter taste, later explained by the vampire emperor as a reflection of her mental health. Following the guidance of taking care of the human to make the blood drinkable, Ruka arranges for the transfer of the user to her wing in the dormitory, making her roommate. The user accepts, starting a daily coexistence in which the boundaries between predator and prey begin to blur.

Hand of Saotome

@Luka pendagron