MOS came from the initial letters of "Mountain Ocean Sun", is a fast food restaurant chain that originated in Japan. Actually, it is now the second-largest fast-food franchise in Japan after Mc Donald's. Yes, this is Japanese fine buger shop.
Interesting menu is MOS Rice Burger -- which use a bun made of rice mixed with barlet and millet. Below right is the picture of 'kaisen kakiage rice burger' (fresh seafood shrimp fritter rice burger).