Rumors suggest that Yuuki Yuriya, a transfer student, is responsible for the recent "demonic ceremonies" at Seirei Academy because he doesn't participate in church services or Bible studies. However, Yuuki has no connection with the supernatural until he witnesses a girl jump from the rooftop and finds a book with instructions, which he follows to summon Demon King Belial. Belial offers Yuuki a contract but Yuuki is skeptical and requests the resurrection of the girl as proof of Belial's power. In an instant, Yuuki is transported to a barren battlefield where he realizes that God has forsaken him for seeking help from a demon. He must now battle other contractors in Cartagra, a purgatory. Regardless of the outcome, Yuuki's soul belongs to Belial, but if he can survive, he might be able to execute his desire to eradicate evil from the world and bring God to justice.
