We stopped for lunch in Shakotan, a town known for its stunning capes, reefs and blue waters that are part of a marine sanctuary. We chose Fuku Zushi, a modest sushi bar that, based on the pictures on the walls, had been featured on television shows.

At the counter, I ordered sanshoku chirashi (2,100 yen, or $21.50 at 98 yen to the dollar), a lacquer bowl filled with uni, ikura, or salmon eggs, and hotate, or scallops, on a bed of rice with wasabi, mint leaf, sliced cucumber, ginger and pickles. The ikura popped in my mouth, the hotate was buttery soft and the uni was creamy and sweet without a seafood aftertaste, the kind of freshness I was hoping we would encounter when we left Tokyo.

There are more than 100 varieties of sea urchin in Japan, but only six are edible. The chef, Kiichi Sasaki, explained that two types are caught nearby: Murasaki uni, which has a mustard yellow color and a sweet taste, as well as longer tentacles on the outside, and bafun uni, which has an orange hue and a richer taste.

Whatever the type, uni is not for everyone. Compared with the meaty red and silver cuts of fish on most sushi plates, uni can taste like briny Jell-O. People who are turned off by the idea of eating roe are unlikely to go for uni, either. But for connoisseurs, Shakotan is the place to be between mid-June and mid-August, when the uni is at its freshest. Mr. Sasaki said some customers visit several times a season.

The uni from Hokkaido is the most prized because of the kombu, or kelp, that they feed on, and the clean water where they live. According to Mr. Sasaki, uni caught along the Shakotan Peninsula “sets the price in Tsukiji,” in Tokyo, where a small box can sell for hundreds of dollars, three to four times more than in Hokkaido. To keep up with demand, Japan imports uni from New England, Russia, China and elsewhere, though Mr. Sasaki said these varieties were not as sweet.

While locally caught fish is often preferred, the Japanese have become anxious about the contamination of their food supply in the wake of the nuclear crisis in Fukushima. But Mr. Sasaki, the third generation in his family to run the 62-year-old sushi bar, said that fish caught in the Sea of Japan, on the opposite side of the country from Fukushima, was safe.