masuzushi

is a kind of Japanese ekiben boxed meal sold on trains and train stations in Japan. It is a type of oshizushi (pressed sushi) and a well-known souvenir of Toyama.

Masuzushi is made of vinegared trout sashimi on top of vinegared rice and wrapped in bamboo leaves. Once the fish and rice is wrapped in bamboo leaves, a weight (often a heavy stone) is kept on top for several hours in order to compress and complete the dish. It is traditionally kept in a round bentwood box known as a mage-wappa, which is then sealed by two bamboo sticks. There are also masuzushi which consist of two layers of fish and rice.