Long ago, a momentary mistake awakened ancient monsters that had been sleeping deep underground. They moved toward the surface with unstoppable force, and endless darkness was about to engulf the world. The player was trapped in a huge dark maze, and while wandering around looking for a way out, he discovered a mysterious gun imbued with mysterious power. This weapon was no ordinary weapon. It was a clue to defeat the monsters, and a key to finding an ancient artifact.