Probably you will be surprised to see this page. There is almost no regulation in salt water fishing in Japan. There are a few regulations in fresh water fishing. Regulations are different in Prefectures. But difference is small. I show you regulations in Niigata Prefectures for example.
Japanese native trouts are Iwana ( Japanese char ) and Yamame trout. These are favorite game fishes in Japan.
Salmon fishing is prohibited. Some anglers enjoy salmon fishing secretly.
Large mouth and small mouth are considered to be harmful fishes in Japan. Because these eat native Japanese fishes and other living things. These are considered to be destroyers of Japanese ecological environment.
There is no regulation of coarse fishing.
I can not find any available website about regulations written in English. When you want to know more about them , contact me. firstname.lastname@example.org.