Masu means 'trout'. This oshi sushi is a very traditional regional food, originally from the Toyama prefecture in the mid-west of Japan. It is famously sold in bento boxes at stations, and is simple but very tasty. Traditionally, round wooden moulds are used, and the sushi is wrapped in bamboo leaves.

Types of maki: Inside rolls refer to the maki that rolls the rice inside the seaweed, or whatever medium you use to roll. There are 3 kinds: hosomaki, chumaki, and futomaki.

Sushi refers to food made with cold boiled rice moistened with rice vinegar and shaped into bite-sized portions. Maki is a type of sushi that is made by rolling the rice around strips of vegetables or raw fish and then slicing the resulting tube into bite-sized pieces. It comes from the Japanese word maku "to roll up."

A Maki (Makiushi) is a traditional sushi roll that consists of fish, vegetables, rice and rolled up in a seaweed. The sushi roll will sometimes include various sauces and the meat can be either cooked or raw.