She doesn't call her "china", could it be a reference to the "chinamen" from detective novels? Do they call it the same in Japan?

Patchouli said:
So you can't go in if you don't knock... then this means it's a locked room murder!

"Nobody could enter without knocking first" (ignoring for now the whole "you don't have to follow the sign's directions" part) = "Nobody could enter or exit"

LOGIC!

This makes me want to see Rapattu do a parody on Hyouka.

NWSiaCB said:

"Nobody could enter without knocking first" (ignoring for now the whole "you don't have to follow the sign's directions" part) = "Nobody could enter or exit"

LOGIC!

dude, you lose if you try to logic things in gensokyo