All salt produced in Japan comes from sea water, there are no salt deposits in the country. The old method starts by first producing a heavily condensed saline solution (brine) from sea water through the use of so-called salt-terraces on the beach (located around the Inland Sea or on the Noto Peninsula), and then by boiling down this solution to yield a residue of edible sea salt (evaporation is not sufficient as Japan is too humid: the brine has to be boiled). Nowadays, salt is extracted from sea water via electrolysis (ion-exchange system).
[Salt terraces, not in use anymore, in Ako, Hyogo Pref.,
a traditional salt producing town on the Inland Sea]
Until 1985 salt was exclusively sold in Japan under a government monopoly. Since 2002 it has been completely liberalized. Most salt produced in Japan is used as table salt. The much greater demand for industrial salt (80% of the total) is filled with imports.
The Japanese intake of salt is high, but this is mainly via soy sauce, miso paste and tsukemono. You won't find table salt on the table in Japanese-style restaurants! Salt is sometimes used with tempura (instead of the dipping sauce) as well as with yakitori. Shioyaki is a way of grilling fish by covering it in thick salt to avoid charring.
Salt plays a ritual use for purification and protection from evil in Japanese culture (kiyome no shio). Take for example the scattering of salt at the start of a sumo match. Another interesting way of using salt can be seen in the small heaps of salt (morijio) placed at the entrance to bars in entertainment districts. Salt for use in rituals in the Ise Shrine is still produced in the traditional way, with salt terraces.