Midori, a VTuber, has just moved into a cheap one-room apartment in Tokyo.

Furnished, appliances included, not even a stigmatized property — she was relieved, for a moment.

But then she finds a single letter left on top of the washing machine.

"If anyone is reading this, whatever you do — don't look in the mirror. Leave now."

"If you've already looked into it... you can no longer leave this room."

"But there is one way out."