Here is an overview of the story, via its official website:
The universe exists, and as it approaches its end, a decision is trying to rest on a newcomer.
By nature, all humans have are prayers. And those prayers are never answered. That is a type of purity.
Is there light on the other side? Or…?
It was the day school-refuser Tsukizaki showed up for the first time, without any warning, to Hasuue Daiichi High School.
She had dazzlingly-dyed blond hair, lifeless skin the color of white porcelain, and dark, cold eyes as if sunk to the bottom of a well.
She did not allow anyone to get close to her.