Uni traditionally is divided into three grades based on flavor, color, and freshness. Grade A is the highest and most expensive, while grade C is considered less desirable, and grade B is in the middle.
Most of the world’s uni is eaten in Japan. There and throughout North America and other areas in the Japanese diaspora, uni is often eaten on nigiri sushi or by itself as sashimi. Elsewhere, it’s also used in many ways in different Mediterranean dishes and other cuisines throughout the Pacific Rim.
Uwajimaya’s refrigerated section within the seafood department carries fresh uni or, when live sea urchins are in season, you can purchase those and harvest the roe yourself.