Jars of "Aji Shio" at a local convenience market. It's the only type of salt on offer.
One of the many mistakes that foreign folks make early on in their stay in Japan is buying salt with MSG or MSG instead of salt to put on their food. Unless you know what it is, they look very similar and are not marked in an appreciably different fashion. In fact, in many convenience stores, they don't sell shakers of regular salt and only sell "Aji Shio", which is salt with MSG. While I don't believe MSG is dangerous, I don't like the taste of it and it can have bad side effects like causing headaches.
I won't miss the liberal addition of MSG to processed and restaurant foods in Japan nor the difficulty of getting salt without it at certain shops.