Alfred, a disgraced alchemist, is cast out of his workshop and finds himself wandering the mysterious city of Luvilia, a place where supernatural beings gather. Desperate and alone at night, he is approached by a beautiful nobleman who offers him a chocolate drink. Hoping to get close to this wealthy patron, Alfred accepts, only to discover the man is Shin, the most powerful vampire king. Alfred has his blood drained and is taken prisoner in Shin's residence as little more than livestock. The only condition for his release from this forced master-servant contract is a seemingly impossible demand: make the ultimate chocolate.

The key to breaking the contract lies in Shin's singular weakness, a blissful sense of being alive that he craves. Forced to put his dignity and pride as an alchemist on the line, Alfred must now master the art of chocolate-making to satisfy his immortal captor. What unfolds is a tense and sweetly dangerous battle of wills. Shin finds his captive's murderous intent alluring, while Alfred constantly wishes death upon the vampire who enslaved him. As Alfred experiments with recipes, the central question becomes whether he can kill Shin first with a supremely sweet morsel or if he will be broken and become his servant forever.