Abalone
Abalones are known as the most expensive among the shellfish toppings in Japan. One of the reasons is probably they are difficult to find; they live deep in the sea, on (or between) the rocks among seaweed and many small living creatures, and they also carry seaweed or these tiny creatures on their shells to camouflage themselves as rocks (or just by chance?). Traditionally, it is a job of female divers called “ama” to catch abalones living in such environment. They dive into the ocean, search for abalones, and get them one by one. It is a very tough work; diving while wearing Japanese cotton clothes*, and without oxygen supply. No wonder the price of abalones are the highest!
*Nowadays, they wear a wet suit except for special occasions such as a rite or a event.

Another aspect of abalone is that it is a sacred shellfish which, for more than 2000 years, have been offered annually to the Gods of the Ise Shrine (a shrine which has a deep connection to the Japanese Imperial Family). Every year on the 1st of June (based on the Japanese lunar calendar, that was in effect until about 100 years ago), a rite related with the abalone is held; local female divers catch the first abalones of the season. The abalones are then made into “noshi-awabi*” by the local elder men, and dedicated to the Ise Shrine.
*Abalones are cut into long, thin slices, dried under the sun, and rolled out to make them much thinner. “Noshi-awabi” was considered to be the earth’s supreme gift; eating it will assure people of receiving God’s grace.

(Reference: http://hyoukichiya.com/noshi.html)

Nowadays, we can see abalone on the menu list even at conveyer belt sushi restaurants, thanks to the possibility of raising abalones using modern farming techniques. But it is still more expensive than other shellfish, and you might have to tell the sushi chef personally to prepare it just for you (if you see cheap abalones going around and around on the conveyor belt, they might not be abalones at all, but rather, a similar shellfish). The abalone topping is cream-colored with thick gray fringe. The texture is crunchy and tough: it is crunchy at first, but it is also a little tough, so that you cannot chew it up easily and it will remain in your mouth longer.