A new requirement that shoppers pay for plastic bags — previously distributed free of charge — has compelled many of them to bring their own bags to put their purchases in. But the charge, implemented nationwide in July, has come at the cost of an undesirable side effect: a rise in shoplifting.

More and more customers are now taking advantage of their own personal, reusable bags, which they are encouraged to use in lieu of single-use plastic bags, to conceal unpaid items, making shoplifting harder to identify — a headache for shop owners.

The mandatory levy on plastic bags, introduced as part of Japan’s efforts to reduce plastic waste, has led to the prevalence of these reusable bags, dubbed “My Bag.”