Campione! Matsurowanu Kamigami to Kamigoroshi no Maou

Synopsis

In Sardinia, Godou Kusanagi plans to return a stone grimiore entrusted by his grandfather back to former owner, Lucrezia Zora. However, Erica Blandelli, a knight of the Copper Black Cross, threatens him to hand over the grimoire. They are drawn into the battle between a boar summoned by the rogue god Verethragna, and Erica duels with them. Godou attempts to find Erica but runs into Verethragna. When Godou explains that he is delivering the grimoire to Lucrezia, Verethragna flees. Unable to stop the boar, Erica is rescued by Godou. Later, after discovering that Godou is planning to deliver the grimoire to Lucrezia, they go to her house, accompanied by Erica's maid Arianna Hayama Arialdi. While there, Lucrezia reveals that the grimoire is based on the book of Prometheus and has Godou keep it. The next day, Erica and Godou encounter Melqart, another rogue god. Having learned of the ten incarnations from Lucrezia, Godou asks Melqart to form an alliance with him. Using the grimoire, Godou steals Verethragna's golden sword and kills him, therefore he becomes a Campione, a god slayer.

(Source: Wikipedia)