A strange group of cultists have begun to gather a black mass in hopes of reviving an ancient devil lord known as Dante. Ryō Utsugi, a high school student, begins suffering strange dreams and premonitions. Soon after, Ryō's sister, Saori, is kidnapped by these cultists for use in their sacrificial ceremony in hopes of reawakening Dante. Ryō's premonitions guide him to the ceremony, and just before Saori is to be killed, the cultist's ceremony is disrupted by a force of holy men. This happens just in time for Ryō to save his sister from her fate.
Believing that Ryō's new-found powers could ultimately awaken Dante, the cultists cause a chain of events that lures Ryō high into the mountains, where he discovers a portal that takes him deep into the Himalayas and into Dante's prison. The devil lord Dante is presented as a giant monster similar to the size of Godzilla, but with bird-like legs, massive bat wings, and a tiny human face between the eyes. Using telekinetic powers, Dante uses Ryō to free himself from his ice prison, before consuming Ryō's body. The cultists then call another black mass together, and they summon Dante, only to find that Dante's mind has been conquered by Ryō Utsugi. Blinded by the rage of his new body, Ryō starts rampaging through Japan.
Later on, Saori has become the tool of God. God is seen as a villain in the series and the cultists are trying to stop God from allowing the apocalypse to occur. Demon Lord Satan is also awakened and helps Dante (Ryo)in his battle against God and his angels. Saori is transformed into an ultimate being, who is controlled by God himself. She battles Ryo fiercely, but they both stop, and they reunite as Adam and Eve. The final scene of the show shows them holding hands and walking in what seems as the Garden of Eden.