Island Sushi or shima sushi (shimazushi) is a type of sushi local to the Hachijyo island located about 150 miles south of Tokyo.
This is a very close style to the Edo style sushi and is strongly influenced by it.
The only difference is that they immerse all their sliced fish in soy sauce, which is sometimes infused with green chili peppers.
Also hot mustard is used as a condiment instead of wasabi, which dates back to a custom when wasabi was unavailable to the island in the old days.
Shimazushi is also nicknamed bekko sushi or amber sushi, for the soy sauce makes the fish a shiny brown color. (Image is red snapper sushi immersed in soy sauce)