In a dystopian post-apocalyptic world where a mysterious blue snow falls and instantly freezes everything it touches, humanity has long forgotten what true warmth feels like. Seonu is a teenage boy living with a prosthetic leg, struggling to survive alongside a young neighborhood girl named Iseo, whom he protects. When tragedy strikes and Iseo loses her life to the unforgiving frost, Seonu refuses to let her rest in the barren wilderness. Bound by a lingering, desperate promise, he hoists her body onto his back and sets off on an grueling journey southward through the deep drifts. Though the howling blizzards threaten to instantly erase his footsteps, his resolve remains frozen in time as he attempts to bring her home one last time.