After being diagnosed with multiple sclerosis, young scientist Reito Mizuhara faces a critical decision: undergo cryosleep until a cure is discovered. In a rush, he opens his heart to his childhood crush Erisa Tachibana and bids farewell to loved ones. As Reito drifts into slumber, Erisa bursts in, promising to await his awakening. Awakening five years later, he emerges to a post-apocalyptic world devastated by the