Japan is a kingdom of snack lovers. Variation of snacks sold in supermarket is wider than in Europe. Therefore you will be in trouble what to buy in Japan.
Especially if you like rice crackers than potato chips, you will be deep trouble. There are many kind of rice crackers. Rice crackers can be divided into two big groups. Senbei and Okaki. Then, smaller type of Okaki is called Arare.
The difference can be the shape. Senbei is round and bigger but Okaki is rectangle and smaller. In addition to the size, the ingredient is different. Senbei uses normal rice which you eat at home but Okaki uses glutinous rice which is sticky.
Senbei can be found on streets, sold per piece at senbei stores. On the other hand, Okaki and Arare are sold per bag. Just watch out when you are taking them back to Europe. They are easy to be cracked.....