Japanese retailers like to offer "fukubukuro" (lucky bags) to customers as an added attraction. The bags, sold at a fixed price, are filled with an assortment of goods that are supposed to be worth more than what you paid for the bag.
But you cannot tell what is actually inside until you have made your purchase and broken the seal.
The "lucky" in the name implies a nice surprise is in store. But there is always the possibility of disappointment. The risk is yours to take or leave.