Abandoned by her parents, Mebachi Higashigumo is mistreated by her foster parents. Then one day, she is suddenly attacked by a "vampire," a demon that lurks in this world. She recalls the days of oppression and almost gives up on life, but at that moment, she is attacked by a vampire, a demon that lurks in this world! "I will change you. I will change you, and in return, I want your lifeblood!" Another vampire offers him a "blood contract"!?