In Japan, sample products are often on displayed for people to be able to actually see what the product looks like. Make sure to check the sample of the product you wish to buy before buying it. Once you open a product that is not a sample, it is considered used and it may no longer be sold to other consumers. Be sure not to open any product other than a sample.
Even if you intend to purchase the item, you should not open the product before paying for it. If you want to make sure that the product you are about to buy is not counterfeit or broken, speak to the staff at the store.