The heroine, Komori Yui, was a normal teenage girl. In her second year of high school, Yui's father, a priest, moves somewhere else for his work. As a result, Yui is forced to move to a new town and arrives alone at a mansion she was told will be her new home. As she approaches the front door it begins to rain. Because no one answers her knock, she reaches for the knob, but the door swings open of its own accord. Yui enters the mansion to find no one in sight. As she starts to explore her immediate surroundings, she finds a young man(Ayato) asleep on a couch. He wakes up as she approaches him and promptly pins her down. As she begins to panic, five other young men gradually appear. Yui notices something different about all of them. She discovers that all six of them are brothers but by three different mothers, later revealed to be Beatrix (mother to Shu and Reiji), Cordelia (mother of the triplets Ayato, Kanato, and Raito), and Christa (mother to Subaru). However, these young men don't seem quite human. In fact, they all turn out to be vampires.
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