Karei – sole, flounder:
さざえ sazae, turban shell:
Sea urchin is edible, it is a sushi item and it is called uni in Japanese. To maintain a thin and fit body, many study calorie-related books and are aware of the food nutritional facts in Japan. Sea urchin has as low as 120 calories per 100 grams, and is rich in omega-3 fatty acids, which makes it popular.
Uni looks like this inside - it is a photo taken in Hokkaido, where it can be found more easily: