This is a missable achievement during chapter 12.
This is a guide from psnprofiles.
In Chapter 12, there's a sequence inside the Benten Inn where you fight your way through hordes of Nikkyo Consortium thugs. The safe related to this achievement is found towards the end of the sequence, next to the second set of stairs, just after you fight the enemy dual-wielding the fans. Before climbing the stairs, go to the room just to the right and you'll find two white safes in the back left corner. It will look like this:
Keep hitting the safe until it breaks open (the Breaker battle style is the fastest at doing this). When the safe has been destroyed, you will receive a large amount of money, along with this achievement.