Third week's prompt! As soon as I saw this quote from the fanbook, I knew I wanted to see what fandom would do with it.
Kirie - "We also planned on having the beams of the Buddha Room lead to a hidden passage to the Koto Room, where Miku would meet Kirie's mother, who hid her from the people of the Himuro family." (Source)
I hope it fires up your imaginations like it did mine! Note: I only put Kirie in the subject like for simplicity's sake, but she doesn't have to be the focus. You can concentrate on Miku, Kirie's mother, Himuro OCs, whatever.