Kusanagi Godou is entrusted with a stone grimiore by his grandfather to deliver to its former owner, an old friend, in Italy where he encounters supernatural happenings. Meeting the beautiful knight, Erica Blandelli, he is drawn into the battle between rogue gods, and uses the power of the grimiore to defeat the Persian god of victory, Verethragna, gaining his powers, becoming a god slayer, also known as a Campione.

Godou wakes with an unexpected guest in his bed, a guest that is here to stay.

Athena has come to Japan looking for Medusa and for that Godou will have to die, again.

Godou will have to set aside his pacifist ways and go full on attack against the newly restored Athena.

Yuri is growing closer to Godou and sparks of jealousy fly from Erica. But that is the least of problems considering there is a new Campione in Japan.

Godou has picked a fight with one of the oldest and strongest Campiones, Voban.

Voban has caught up and Godou is running out of ideas. Mariya makes the ultimate sacrifice, in front of Erica.