Fermented food products are said to be good for your health, and perhaps the ultimate example is Shiga Prefecture’s unique Funazushi.
Funazushi is made from the Nigoro-buna fish, also known as the “round crucian carp”, which is only found in Lake Biwa. Combined with rice, it is then fermented, and is also said to be the origin of sushi.
It was created as a way to preserve fish in a time before refrigerators existed, and seems to be eaten during the Heian period (794 - 1185).
Although some people don’t like its unique smell, it can be enjoyed accompanied with some Japanese sake, just like blue cheese!

List to stores where funazushi can be purchased:
Sakamotoya https://en.biwako-visitors.jp/spot/detail/47
Hisagozushi https://en.biwako-visitors.jp/spot/detail/174

A video from Only in Japan “This is Funazushi!”:
https://www.youtube.com/watch?v=EI5Jv5PCctA