Nightmare Mansion [Final] [Tsuyoi Ko]

An illness called “Nightmare” is infecting young girls, making them unable to awaken after sleep.
As the patients show only healthy signs, a countermeasure can’t be developed.

One day, Sana is hit with “Nightmare”, and suddenly finds herself in a mysterious mansion, along with her close friend Tomo.
What will they find in this abnormal place, and what will they choose?