Episode 1

In Sardinia, Godou Kusanagi plans to return a stone tablet entrusted by his grandfather back to its former owner named Lucrezia Zora. However, Erica Blandelli, a knight of the Copper Black Cross, threatens him to hand over the stone tablet, calling it a grimoire. When a boar is summoned by a rogue god named Verethragna, Erica fights it. Attempting to find Erica, Godou runs into Verethragna, who flees after Godou explains that he is delivering the grimoire to someone. Although Erica is unable to stop the boar in time, Godou rescues her before the boar disappears. Erica later discovers that Godou is delivering the grimoire to Lucrezia, and Erica's maid Arianna Hayama Arialdi accompanies them to Lucrezia's house. While there, Lucrezia reveals that the grimoire is based on the book of Prometheus, telling Godou to look after it. The next day, Godou and Erica encounter another rogue god named Melqart. Having learned of the ten incarnations from the grimoire, Godou asks Melqart to form an alliance against Verethragna. Using the grimoire, Godou steals Verethragna's golden sword. After kissing Erica, Godou kills Verethragna using the Warrior, therefore becoming a god slayer known as a Campione.