>>49428248
Here's the hall by the way. Kasen's study/room where she usually talks to Komachi is on the 3rd floor, I think.
Other pages from earlier in the manga seem to imply that there's 2 windows on each side of the building and per floor, so these 4 rooms on the inside are probably all there is, aside from a staircase or something somewhere in the back of the building.
I wonder if the "balcony" around each floor has some kind of door out to them, the windows are big but I don't think you're supposed to enter and exit through them.