The reason why sea urchin in Hokkaido is more delicious than sea urchin from elsewhere is the abundance and freshness of sustenance such as "Rishiri kelp" and "Hosome kelp" exist on the market as luxury products.
Uni Grading System
Like any premium product, Uni pricing is based on its grading. This is especially true for Uni headed to the Uni Auction Market, where auctioneers trade hundreds of Uni every morning.
Uni auctioneers determine Uni grading by color and texture, and those closer to having a golden color or more discernible bumps on the surface merit more value.