It is simply made with salt from Tsushima, Nagasaki, which is boiled in a pot, and is soft even to the bone. 
Chiba Sanchoku Service's "Toro Sanma Boiled in Water 150g" is a canned product made with carefully selected fresh seasonal saury caught off the coast of Sanriku from Hokkaido. It is made with seasonal saury that is particularly fatty, and only high-quality fish that can be served at sushi restaurants and traditional Japanese restaurants are used. Since it is produced in limited quantities for a few days a year, they are particular about the freshness and quality of the ingredients, and may reduce production if they are not judged to be of the highest quality. The cooking is very simple, using only salt from Tsushima, Nagasaki, which is boiled in water, making the most of the flavor of the ingredients. It is soft even to the bone, has no fishy smell, and allows you to enjoy the deliciousness of seasonal saury as it is. Since it is only seasoned with salt, you can enjoy the original umami of the saury directly.

Product Specifications for Chiba Direct Service Boiled Fatty Sanma 150g