Hikarimono refers to sushi toppings made from fish such as kohada, aji, saba, kisu, sayori, kasago, iwashi, and sanma, which have blue backs and silver-white bellies. Because they tend to lose freshness quickly, when used for nigiri sushi, the fish is usually salted and left to rest for a while, followed by a “vinegar-marinating” process. However, in recent years, due to improvements in storage conditions during distribution, mackerel, horse mackerel, and saury are often served as sushi without being marinated.