Komori Yui is an optimistic young lady that has a strong connection with her father. When he allegedly has to travel for work purposes, Yui is sent to what she thinks is the residence of some distant family members. She is immediately greeted by six strange young gentlemen, the Sakamaki brothers, all of whom want one thing from Yui--her blood. Yui must learn to adapt to life while being a constant target of six forceful vampires, as well as uncover Sakamaki family secrets and information about her role and identity.