In Japan, tax-free items—specifically consumables like snacks, cosmetics, and medicine—are sealed in special tamper-evident plastic bags at the point of purchase. The legal requirement is that these bags remain sealed until you leave Japan. If you open the bag and consume or use the items within the country, you are technically in violation of tax law. At the airport, if customs officials inspect your luggage and find the seal broken or the items missing, you will be required to pay the 10% consumption tax on those items immediately. While physical inspections of every tourist are rare, the "tax-free" status is granted on the condition of export; thus, opening the bag "voids" the tax exemption. Non-consumable items (like clothing or electronics) are often not sealed in these bags and can be used in Japan, provided they still leave the country with you.