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The Boutique is a location in Luigi's Mansion 3. It is found on the first level of the Hotel Shops. It is right of the Barber Shop and below the Gift Shop. The red gem can be found here. This is the second shop Gooigi needs to explore. Due to there being bars in the door, only Gooigi can explore it. The first Mini Goobs in the game are encountered and fought here.
After getting the heart key from the Accessories, Gooigi must enter the boutique and open the cash register to get the spade key which opens the register in the gift shop. Once he gets the key, however, it begins floating and disappears behind the wall. Gooigi needs to flash the green light revealed behind the register with the Strobulb to reveal a large pile of coins. As he collects them, a Mini Goob appears and signals more. Gooigi must defeat them to reveal the key.
There are coats hanging near the southeast corner. Gooigi can pull the chain in the northeast corner to reveal an embarrassed Goob. There is also a drain Gooigi can go through to get coins. There are two mannequins near the north wall Gooigi can use the Suction Shot on to get treasure. There is a safe behind the wall.
To get the red gem, Gooigi must use the Suction Shot on a mannequin near the southwest corner to open a secret compartment with both a treasure chest and the gem.