While you were supposed to be exploring the vacant lot of an abandoned shopping mall, the ground suddenly gives way beneath your feet and you fall into somewhere unknown.

After a dizzying fall, you awaken to find yourself in a vast, uninhabited space where the walls, floor, and ceiling are all yellow.

In this place you thought was deserted, there is a woman around your age. She has a flashy appearance with silver hair in a ponytail. It seems you've ended up alone with this woman in this strange, exitless space.