Eight years ago, an unknown catastrophe called (“Demonization”) struck the world. It is a calamity that seals off parts of reality and overwrites them with a nightmare realm—if you cannot survive, only a cruel death awaits. In this changed world, Yūgo Fushimi lives a quiet, withdrawn life, limiting his outings to commuting between home and work. Gentle, timid, and overly sensitive to others’ pain, he is always sleep‑deprived and often late, leading his coworkers to mock him as a “clumsy do-gooder” and a “shut‑in introvert.” One day, he is forcibly dragged out to a drinking party—and there, he witnesses the horror of Demonization firsthand. The city is trampled, people scream and cry, his coworkers collapse one after another, and grotesque enemies flood the area as it transforms into a demon realm where survival seems impossible. At that moment, in the midst of despair, Yūgo alone grips his weapon as if remembering something long forgotten—hinting that he may be a “returner,” someone with a hidden past connection to this nightmare and the power to fight back.