Tomboy Bandit is a quest in Final Fantasy VII Remake that you can complete in Chapter 14. This quest is needed to complete other quests in Final Fantasy VII Remake.
You can start this quest by talking to Johnny at the station in Sector 5.
He says he has been mugged by a person matching Kyrie's description. Kyrie is also needed for the quest Corneo's Secret Stash, so completing this quest will also allow you to progress in that quest.
You can find Kyrie at Aerith's Church. She tells you she is being chased by Shinra and that she will return what she stole if you help her out.
You will need to go to the Coliseum in Wall Market and fight the Special Match that should now be available.
You will have to fight Beastamer and his pet Hellhound. The fight is quite easy; take out the Beastmaster first and then focus on the Hellhound.
The Hellhound is weak to Ice Materia. Using Ice will also weaken their attacks.
After you defeat the Hellhound, you can return to Kyrie. Her Grandma Mireille shows up also and scolds her. You will get Johnny's Wallet back and Corneo's Vault Key.
You can also complete a Discovery Quest by going back to Johnny and giving him his wallet.