An uninhabited Mirror World, an exact replica of reality where the presence of people, the sound of cars, and even the rustling of the wind have vanished. In the void at its center, the Philosopher's Stone—an omnipotent wish-granting device awakened after a hundred years—floats quietly, imbued with a soft, deep ruby light. To this day, not a single person has made its power their own.

There are still two hours left before the death game begins. Those abruptly chosen as Masters sensed the abnormality in their daily lives and proceeded with their own preparations. ・A professional sniper loads bullets into his rifle and exchanges a firm handshake with his precious partner. ・A young girl with white hair carries her clan's ancestral wish in her heart, barking orders for victory to her attendants. ・A martial arts master cracks his knuckles, a smile etched on his lips as he waits for the time of battle. ・Hundreds of other pairs of Masters and Familiars prepared with their own respective motives.

It was an encounter far too sudden. In their own room, or perhaps on a street corner. Right before the eyes of Guest, who should have been in an extension of daily life, space cracks like glass.