Also, people are economically in a pretty bad place here, borders are still closed with no sign of opening. It might be a long shot but Abenomics was all about making Japan a "service economy", that relied heavily on tourism. No tourists, no money. Maybe a link there? Maybe Yakuza? Maybe the guy was just totally crazy and had trouble getting mental health assistance (which is also hard to get in Japan).
Japan is basically a one party state, it's advertised as a democracy but it's not really. I guess people feel desperate and there's no sign of any healthy change on the horizon. I guess that might be part of it too.
Shinzo Abe was a leader of the LDP which is the dominate party with no sign of that changing within the next few decades. It could feel oppressive for people.
Condolences to his family and friends.
I think you might be onto something with the Yakuza, could be foreign activity as well.
https://www.unilad.co.uk/wp-content/uploads/2020/10/Narita-A...
What's interesting is that flights are actually now relocating back from Narita to Haneda, which was over capacity at the time, but Haneda has since added more capacity.
For reference: https://en.wikipedia.org/wiki/Abenomics#Results
So yes, he basically froze who would be the winners and losers for the span of his policy, and low income people didn't feel great about it.
I have my gripes yet still think he was a more decent PM than many previous ones. It's really sad it comes down to an assassination in the end.
[0] https://tradingeconomics.com/japan/gdp-growth [1] https://wid.world/country/japan/