Ark shell (akagai) is called the “yokozuna of shellfish” and is an essential sushi topping (neta). In old times, akagai from the mouth of the Kamigawa River was said to be the most excellent and sushi chefs used to call all akagai “kamigawa”. It is said that akagai received its name, which literally means “red clam”, because it bleeds like a fish when cut with a knife. In winter, akagai grows and becomes more flavorful. Its ribbon-like edge is especially enjoyed by akagai lovers for its slightly sinewy texture.