Koi Shita Hito wa, Imouto no Kawari ni Shindekure to Itta.

In a world teetering on the brink of an unknown catastrophe, a young woman finds herself entangled in a harrowing prophecy. The boy she loves, burdened by a terrible secret and an impossible choice, makes a request that shatters her reality: to die in place of his sister. This isn't just a tale of star-crossed lovers, but a profound exploration of sacrifice, destiny, and the lengths one will go to for those they cherish. As ancient powers stir and a looming darkness threatens to consume all, she must navigate a treacherous path where love and duty collide. Will her heart guide her to an unimaginable act of selflessness, or will she defy fate to forge her own destiny? This dramatic fantasy weaves a poignant romance into an epic struggle for survival, promising a journey filled with heartache and heroism.

✦ AI-drafted summary