Considering that it's Aoshima, the reason for the specificity isn't to say that she's turning away straight people so much as to say, "Sex goes on, here."
Anyway, I like Koa The Elder, here. Aoshima tends to make the deliberately sexy characters completely overplay their hand.
The Librarian (Daytime)
Koakuma (the Elder)The Librarian (Nighttime)
Koakuma (the Younger)My, how rare.Takes her job seriously.
The Short-Haired KoakumaNegligent WorkerSecretly runs a lesbian bar in the corner of the library.
The Long-Haired Koakuma....You're very harsh-ze....Koa
You're here to borrow books?To start with, you need to pay your debts for all the books you've borrowed without notice up to now, please.The total is 564 books ♪