Synthetic Gods Game: I Am the Undying Berserker

Tyler Newman delivers packages. His younger sister has been taken by people he cannot reach, and his childhood friend is the one person still close to him. This happens in an age when the gods hand out fragments of divinity and people awaken to the powers inside them. Tyler runs into the assassin Mandy Hayes and she cuts his head off. At the point of dying he awakens an SSS-rank fragment, the Headless God, and comes back with the strength of a war god. When he and his childhood friend are cornered, they are saved by Nora Shaw, who heads the Horizon Guild, and Tyler becomes her bodyguard. From there he goes after the men holding his sister.