Shu Sakamaki is the first and eldest son of the Sakamaki household. He is also the current master of the mansion. Shu and his younger brother, Reiji, are the sons of Beatrix, second wife of Karlheinz, the Vampire King.
Since he was the eldest son, despite having all the attentions, he was always alone until he met Edgar, a human in a nearby village, who soon became his best and only friend. When Edgar died, due the big fire in the village, Shu felt it like he was unable to save him and blamed himself. He’s still unaware that the fire was set up by his brother Reiji out of jealousy. Because of his past experience, Shu tends to push Yui away a lot, at first, as he says that humans die too easily.