It's a pure rogue-only perk, giving them special shurikens on rest.
Problem is, being a very niche perk it also requires to take a proficiency feat to even become usable.
Simple solution is to add a free monk weapon proficiency to this perk.
The only difference between rogue proficiency and monk proficiency, if second is added over the first, is shurikens and kamas. And kamas is not something gamebreaking, or even game-altering for a rogues.