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.

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.

A simple trip to the beach turns into war for Godou's affection, which he only manages to escape with the help of Athena. His troubles are only the beginning...

Godou is resting at Liliana's home after his fight with Perseus. He does not have the knowledge to fight Perseus on common ground, Athena visits offering a deal.

Without the knowledge, Godou has no chance of defeating Perseus. He could order Liliana to give him the knowledge but that is not his way. How will Godou defeat this ancient hero?

A maiden has come willingly to join Godou's ranks, but his current Knights have other plans.

In order to save Erica, she must sacrifice herself, body and soul, to Godou.

Godou must battle Metis, the snake goddess of death and darkness. A being that's only goal is to bring destruction to the world.