The Staircase is accessed by opening and entering the zipper in the leftmost room on the first floor of the Red School.
KyuuKyuu is there, rubbing the rail like in the original game. On the first visit, Monoe sits on the stairs crying. A kind of jumpscare-y event takes place and Madotsuki is forced to wake up.
The second time, the stairs are no longer blocked and you may climb them up further and enter a door. The FACE event takes place there.
