Unmissable and story related achievement.
After you exit Hibari's for the first time and get the quest "Fashion Gold", exit West one screen and take the first exit to the North. You'll have to battle your way down nine floors, when you finally get to the bottom take to the pawn shop owner on the right side of the screen to get a Fake Golden Cat and the achievement.
Don't forget to smash the statue of the left side of the pawn shop screen before you exit!