It is illegal to make alcoholic beverages without a license, regardless whether it is for sale or for personal consumption in Japan. And the process of obtaining the license is so difficult and expensive, that it is only worth it for businesses.
In this busy 21st Century, not so many people are interested in brewing their own sake in Japan, and most of them don’t give it serious consideration. But there used to be a man who kept brewing his own doburoku (a crude type of unfiltered sake).
I remember hearing about the news of the “Doburoku Trial” when I was young in 80’s. The old man, Toshihiko Maeda, was saying “What’s wrong with making sake for my own consumption? I am not selling it.” In Japan there is a tax on the production of alcohol. He challenged this tax law based on the fact that he did not sell the sake. Further, he complained that prohibiting the brewing of sake for his personal consumption is against his right of the pursuit of happiness under the Japanese constitution.
The trial gained significant media coverage, but Mr. Maeda lost in the end. The government cited that even for personal consumption, brewing alcohol can reduce the tax revenue of the country. Since then, no one has challenged the law.
In the United States, brewing alcohol for personal consumption does not seem to be illegal. If you are interested, here is a recipe of how to make unpasteurized doburoku (unfiltered sake).