In other countries, it may be possible to return something you buy from a store unconditionally, but in Japan returns are very limited. Unless there is a defect with the item or the staff gave you a false explanation when you bought it, or in some other way the contract of sale was problematic, you cannot return the item giving just any reason you want. You can't just say "I found it cheaper in another store," or "It wasn't what I imagined." Stores may have their own return policy, and in that case, you have to follow their rules. But even if a store accepts the return, you will need to show the receipt, so always keep the receipts of things you buy during your trip, and keep things as new and clean as when you bought them. Also, check the quality and price of a product carefully before buying it, and if you have any questions or concerns, it is important to ask the staff at the store when making the purchase.