It's worth noting a comment on HN points out that the article source is comments during a meeting from a government official.
Looking through the first source, it's not at all clear that this is policy. In fact, that meeting from April 2023 seems to indicate that current copyright protection is insufficient for AI, and new regulation is required.
The second source at the bottom of the article doesn't work for me currently.
Anyone fluent in Japanese would be a welcome commenter here.