The heroine, Yui Komori is a positive-thinking girl who nevertheless is troubled by seeing spirits and experiencing poltergeist phenomena. In her second year of high school, Yui's father, a priest, has to move to overseas due to work and she is not allowed to accompany him. Yui instead is given a certain address by her father and instructed to go there, saying the people living there are "relatives". Yui follows her father's orders and arrives at a mysterious mansion as the address had suggested. As she discovers what's in the house, she meets the six Sakamaki brothers who don't seem "normal" and learns that they are vampires. She ends up having to choose one of them to drink her blood. So begins her journey into the darkness.