Hokkaido is off the tip of the main island, Honshu. It is the northernmost island and has a climate not as mild as the rest of Japan. In the winter, there is snow and temperatures reach freezing levels, while in the summer, it is hot.
Before soy sauce became a preferred seasoning in Japan, there was salt.
One of the original sources of salt in Japan was from animals’ intestines. Another was salt drawn for the sea. However, it was scarce and did not keep for long, so sea salt was commonly mixed with something else that could prolong its shelf life.