TIROL Chocolate 20 yen each
You should go to a Japanese convenience store and buy TIROL chocolate for your friends! TIROL chocolate is very famous and I bet almost everybody knows.
Originally they were introduced to the market 40 years ago and for the time being, they were sold at 10 yen each so that even little children can buy. Now they are sold at 20 yen each, but this is not due to the economy. It is because each of them needed to have barcode on it for easier accounting process and the company decided to make it bigger and raise the price accordingly.
Anyway, they have a variety of flavor and they are cute. So they may be good as souvenirs from Japan!