The main heroine, Yui Komori, was an ordinary teenage girl until in her second year of high school. Her father, a priest, must go overseas for work. As a result, Yui is forced to move to a new town and arrives alone at mansion she was told is going to be her new home. As she approaches the front door it starts to rain. Because nobody answers her knock, she reaches for the knob, but the door swings open of its own accord. Yui enters the mansion to find nobody in sight. As she begins to explore her quick surroundings, she discovers Ayato sleeping on a sofa. He wakes up as she approaches him and rapidly pins her down. As she starts to panic, five other young men gradually show up. Yui realizes something different about all of them. She finds out that all six of them are brothers but by three different mothers, and they all come to be vampires.