Cross Academy is attended by two groups of students: the Day Class and the Night Class. At twilight, when the students of the Day Class return to their dorm, they cross paths with the Night Class on their way to school. Yuki Cross and Zero Kiryu are the Guardians of the school, there to protect the Day Class from the Academy's dark secret: the Night Class is full of vampires. Zero warns Yuki to stay away from Maria Kurenai, the new Night Class transfer...

When the master she has sworn to protect is killed, Mikage Kirio, a skilled ninja, travels to Japan to start a new, peaceful life for herself. But as soon as she arrives, she finds herself fighting to protect the life of Mahito Wakashimatsu, a man who is under attack by a band of ninja. From that time on, Mikage is drawn deeper into the machinations of his powerful family.