That said, I think people need to recognize that in many aspects what's happening is connected to societal issues that gun control and gun regulations will have very little impact on - remember, even in Japan somebody could make some kind of battery ignited home-made shotgun and kill Shinzo Abe.
ok let's try data instead of feels. Per Capita, what is the number of mass shootings per year in the USA, and in Japan. I did't know the answer but asked Gemini.
The most recent year for which there is data, apparently, is 2023, during which there were 604 mass shootings in the USA, and 1 in Japan. Given the respective population counts, the per-capita rate of mass shootings in the United States was about 225 times higher than in Japan.
Given that, are you confident that your observation that "one guy made a gun once in Japan" is a strong refutation of the idea that the US could reduce mass shootings by strengthening regulations?