The Secret Club's Secret

The Secret Club's Secret is a Side Quest in.

Overview
On the side of the Fashion Passion clothing shop in Gerudo Town, Link will find a closed, wooden door. If he attempts to open it, he will receive the Quest and hear the Gerudo Greta speaking, who requires a password for entry. If Link guesses the password wrong, he will not be able to try again until the next day. Greta will then tell Link to go drink milk in the bar as a way to tell him to go away. This actually serves as a hint for where Link can find the password. If Link goes into Gerudo Town's bar, The Noble Canteen, he will find three Gerudo women named Pyra, Sumati and Yaido who are talking about a password. They stop talking about it as soon as they notice that Link is listening. Link must eavesdrop on them by going onto the opposite side of the nearby window in Rotana's house.

If Link eavesdrops on them here before ever speaking to them while in the Noble Canteen, he will hear Yaido asking the others if they have heard of a rumor about Fashion Passion. Sumati replies that she has heard the rumor and Yaido responds by saying that she asked Saula about it, but Saula wouldn't tell her anything. Pyra then mentions how suspicious it is that Saula won't give away any information. If Link has not begun the Quest, this dialogue exchange should direct him to Saula, who will tell Link about the secret entrance to the store.

Once Link is eavesdropping on the Gerudo women after speaking to them directly, he will overhear Sumati referring to him as a little Hylian girl. Pyra then says to forget about the girl and urges Yaido to tell them the password. Yaido reveals that she overheard Saula say that the password is "GSC♦." Sumati quickly realizes that it must stand for "Gerudo Secret Club" before the conversation ends. Once Link returns to the wooden door and tells Greta the password, he will be allowed entry to the Gerudo Secret Club and the Quest will be complete.

Trivia

 * Link does not have to eavesdrop on the Gerudo women in The Noble Canteen to enter the Gerudo Secret Club. He can guess the password, but there are 256 possible answers.