"Campione!" is a light novel series written by Jō Taketsuki and illustrated by Sikorski, later adapted into a manga. The narrative centers around Godou Kusanagi, a high school student who inadvertently becomes a Campione, a "God-Slayer," after defeating the war god Verethragna in a battle. Campiones are individuals who have slain deities and gained immense powers, earning them the title of "Devil Kings" among gods and humans alike. These powers come with significant responsibilities, as Campiones are tasked with maintaining balance between the human world and the divine.

Godou's transformation into a Campione thrusts him into a world of mythological conflicts, where gods from various pantheons—Greek, Norse, Hindu, and others—interact with the human realm. His newfound abilities attract the attention of other Campiones, divine beings, and organizations dedicated to studying or controlling supernatural phenomena. Among these is the History Compilation Committee, a Japanese organization that seeks to manage the influence of gods and Campiones on the human world.

The story explores Godou's struggles to adapt to his role as a Campione while maintaining his moral compass. He is often reluctant to use his powers, preferring to resolve conflicts through diplomacy or minimal force. However, his pacifist tendencies are frequently challenged by the aggressive nature of the gods and other Campiones. Throughout the series, Godou encounters and battles numerous deities, including Athena, the Greek goddess of wisdom and warfare, and Lancelot, a knight from Arthurian legend. Each confrontation reveals more about the intricate relationships between gods, Campiones, and humanity.

Godou is supported by a group of female companions, each with unique abilities and connections to the supernatural. Erica Blandelli, a skilled knight and magician, serves as his primary ally and love interest. Other key characters include Liliana Kranjčar, a rival magician with a strong sense of duty, and Yuri Mariya, a shrine maiden with spiritual powers. These characters contribute to the narrative by aiding Godou in his battles and providing insight into the world of gods and magic.

The series blends action, mythology, and romance, with a focus on the tension between human morality and divine power. Godou's journey as a Campione is marked by his efforts to protect humanity while grappling with the consequences of his actions. The narrative delves into themes of responsibility, sacrifice, and the clash between mortal and immortal perspectives, all set against a backdrop of mythological intrigue and supernatural conflict.