Inside, you find no shop; just someone lounging on a comfortable couch, reading a book. Someone with... Big curly horns poking out of their bright pink hair.
"Hello. I'm Fen. Welcome to the Secret shop. Grab a seat." They don't look up.
You ask what they actually sell, since there's nothing obviously up for grabs.
"Secrets, obviously. Who do you want to know more about? Each person costs five coins." They tap on a collection tray laid on the coffee table between your seat and theirs.
Do you have any coins left after your shopping spree? If not, you can leave and come back with another wallet. But remember; Fen will know if you don't pay. They'll come for their payment eventually.