The story follows Okoyo Takumi, a young man who discovers that his beloved stepsister, Haruna, is being harassed by a stalker. Determined to protect her, Takumi illegally modifies a stun gun into a weapon with the intention of killing the stalker. Before he can act on this plan, the entire school campus is suddenly transported to a parallel fantasy world. The school is immediately overrun by monstrous creatures, chief among them orcs, and descends into a hellish nightmare of slaughter and sexual violence. In the chaos, Takumi and Haruna attempt to flee, but Takumi is killed. He then finds himself back at the moment the school was transported, with his memory of the previous events intact. He realizes that he is trapped in a time loop: every time he dies, he returns to the same starting point. This forces him to repeatedly witness the brutalization and death of the people he cares about, especially Haruna. Imprisoned in this cycle of death and agony, Takumi must use the loop to gain combat experience, level up, and acquire new skills to survive. The loop also grants him a unique perspective, allowing him to experiment with different strategies and make difficult ethical choices in his quest to break free. Over time, he successfully hunts an orc and gains a level, confirming the presence of a game-like system in this world. His initially solitary struggle changes when Haruna's quick thinking helps them rescue a classmate, Isumi Jun, from an orc attack. Jun, who is exceptionally perceptive, quickly deduces that Takumi is reliving the same events. She joins their party, bringing new dynamics and shifting the nature of the fight for survival. The central narrative explores Takumi's crumbling sense of justice as he is forced to weigh love against terrible sins, constantly making sacrifices and confronting the brutal reality of the world, all while trying to navigate the prison of time to secure a future for himself and his loved ones.