Yūki Komori, is the Youngest Sister of Yui Komori, and who was born with a Weak Heart... Also known as "Sugar", she likes to be preferred herself as "Sugar" instead of her real name... Sugar always the Shadow of her Older Sister, Yui. She and Yui treating differently... Yui, the Oldest, they always doting her and praising her because she's "Perfect". And...meanwhile Sugar, the Youngest, always forgotten, like she wasn't even exist and just a Shadow of her Older Sister... One Day... Their Father, Seiji Komori, the Head of the Priest of the Church... He send them to the Sakamaki Mansion for his... "Reasons". But, little they didn't know what awaits them... A Danger? Probably... 6 Mysterious Vampire, the Sons of Karlheinz... "I wonder... What the Future awaits me?" Sugar quietly mumbled to herself.