Thieves

Thieves will only begin appearing after the purchase of the first shop upgrade. They will occasionally enter the store and wander around. After a little while, they will pick up an item and make a mad rush for the door. Will can intercept them with his dodge roll ability, starting a small brawl where he collects his items, depositing them back into his inventory, and the offending customer will leave the store. It is possible for the same thief to return multiple times on the same day, however. If you fail to catch them in time, they will leave with the items. Be aware that thieves can also steal directly from the cash register, so don't just assume they can't steal anything when no items are displayed.

Appearances
Each additional upgrade introduces new thieves with different appearances, meaning Will needs to remember more faces.

Shop Level 1
Small amounts of thieves limited to a guy in a black mask and black shirt.

Shop Level 2
More thieves start to appear including a fat man with an axe and a yellow top.

Shop Level 3
After defeating the carnivorous Mutae, Masa will get annoyed with you because he wanted to defeat it, so he will try to steal from you.

Shop Level 4
While not an actual thief, a bird can fly in through the front window and distract every customer from buying anything until you tackle it.