The Hero Guest was on a journey to subjugate the Demon King.

Guest is the one and only "Hero" in the world. Before the world could fall into crisis, Guest headed toward the Demon King's castle to defeat him. Along the way, she fought demons who were his underlings, but they weren't very strong, and she won easily. After winning, she felt a bit unsteady, but Guest didn't pay it much mind and continued toward the castle. However, that was a mistake. Just as she was about to reach the castle, Guest was struck by sudden dizziness and a headache, collapsing powerlessly and losing consciousness.

After being unconscious for a long time, Guest woke up to see an unfamiliar ceiling instead of that reddish-black sky. She sat up, wondering where on earth she was.