You have to go to the geisha lodge at around midnight for the sandglass. Don't use it as an item - talk to the people there. Also, if you win the sash-undoing competition after midnight, you'll be in for a surprise.
That's what I did, I talked to everyone and also spam that item with everyone at midnight and nothing happened, is there a specific time at midnight where it should be used? Or maybe I already used that item in my playthrough and I just don't remember who accepted the item. In any case, can you please refresh my memory on who accepts the item in the geisha lodge and for what purpose they accepted it? maybe that way I can remember if I used it or not.
And yep, I already saw that surprise at midnight in the sash-undoing competition yesterday, 16-bit uncensored boobies ftw. If this game made it overseas then they would leave that part censored I guess =p
Nevermind, the NPC that accepts the "Sandglass" finally appeared in the Geisha Lodge. It seems she appears at 9:00pm.
My curiosity on using the "Sandglass" payed off, I found 2 typos with the NPC that accepts that item:
First typo: "Sandclass"
Second typo: It should be "sand in it", not "sand it it"