Yoo Kisoo grew up with neglectful and abusive parents who did not care about him whatsoever. The only light in his life was his childhood friend who lived nearby. To Kisoo's misfortune, shortly after they began dating, she heartlessly abandoned him for a popular kid at school. After enduring such a miserable life, Kisoo thought things could not possibly get any worse until the day portals began to appear, accompanied by a game-like system message. People went into the portals, and some never returned. Five years later, every human other than Kisoo has died. Kisoo has only one thought: Finally, I am alone.