Shoko Yobuno, the boss of Zen Amako and Shuichi Aiga, as well as the two laboratory assistants all share a connection to the triangular sacred animal mirror. Despite being pure-blooded siblings, they are oblivious to their demonic ancestry. The mirror will ultimately link with two male demons who possess the same pure-blood status. Zen, one of the demons, will be responsible for the ultimate destruction of the world, while the other demon, Shuichi, will emerge as the savior by defeating Zen.