Gozu's an ordinary guy who gets yanked into a world he actually recognizes—turns out it's the game he played growing up. The catch? He's dead. Well, was dead. Now he's woken up as a hired assassin with one job: kill the demon king Evelogia.
Here's where it gets interesting for him though. Instead of being bummed about the whole "assassin" thing, Gozu's genuinely excited. Evelogia was basically his hero back when he played the game—the only character who ever really inspired him. So yeah, he's supposed to murder his childhood idol, and he's weirdly okay with that at first.
But then something shifts. Gozu actually falls for Eve. Hard. And suddenly his priorities flip completely. Rather than carry out his contract, he starts using his knowledge of how the game's story plays out to change things—specifically to keep Eve from getting killed by the hero, which he knows is coming if the story unfolds the way it did in the game.
So basically, Gozu's trying to be an assassin who saves his target instead of killing her, all while navigating a world that's both familiar and very much real now.
Content compiled by AnimeList.moe from publicly available sources.