Jin Hazama hails from a parallel Japan ruthlessly controlled by Princess Kotoko. Driven by his father's death, he resolves to overthrow her by journeying to another dimension. His strategy centers on eliminating Kotori Izumi, Princess Kotoko's counterpart in this alternate reality, convinced her death will collapse the oppressive regime in his home dimension.

Within this ordinary world, Jin confronts Shin Hazama, his dimensional counterpart. Shin, a high school student grieving his father's recent loss and living with his uncle, finds his life disrupted by Jin's arrival. Jin perceives Kotori—Shin's childhood friend—as an existential menace requiring annihilation, igniting a core conflict between the two counterparts born from shared identity yet opposing lives and objectives.

Pursuing his mission, Jin encounters resistance from forces across both worlds. In the film adaptation *Ashita Sekai ga Owaru Toshitemo*, his goal remains unchanged: killing Kotori to destabilize Princess Kotoko's rule. While the film features a slightly modified plot, Jin's fundamental motivation and role are preserved. Introduced characters like Riko (Miko's sister and Kotoko's fixer) and Genji Hazama (Shin's scientist father) do not significantly alter Jin's path or bring resolution.

Shaped by loss and tyranny, Jin's background offers no suggestion of redemption or moral doubt in his actions. His interactions with Shin starkly contrast their responses to trauma: Jin adopts violence as his solution, while Shin strives to protect his remaining bonds. The narrative confines Jin's development strictly to his unwavering dedication to the mission.