History repeats it would seem, but with a bit of a twist it would seem. I have tried to compile some of the known points of this event. The police seem to have stated that the assassination was not politically motivated.
"The alleged assassin who shot dead Shinzo Abe on Friday believed the former Japanese prime minister was involved in a “specific organization” — and that his grudge wasn’t political, police said. The suspected killer, Tetsuya Yamagami, 41, was tackled to the ground just moments after he allegedly opened fire on the 67-year-old former leader as he delivered a campaign speech in the western region of Nara.
In an interview with investigators, Yamagami allegedly admitted to plotting to kill Abe because he thought the ex-prime minister was connected to an organization that he bore a grudge against. Police did not reveal the name of the organization or elaborate on what it believed in, adding it wasn’t clear if the group even existed. The alleged assassin’s grudge did not appear to be about politics, according to police."
https://nypost.com/2022/07/08/motive-revealed-in-assassination-of-japans-ex-pm-shinzo-abe/
"After his arrest, Yamagami told investigators that he was dissatisfied with Abe and intended to kill him. Yamagami also claimed that he held a grudge against a "particular religious group" and shot Abe because he believed that "the religious group and Abe were connected". The Nara Prefectural Police refused to elaborate on what the "religious group" was. Yamagami claimed that he "didn't have a grudge against Abe's political beliefs"."
https://en.wikipedia.org/wiki/Assassination_of_Shinzo_Abe
So, it would appear that we have a little bit of a puzzle, assuming religion of some sort or another is involved that the press and cops don't want to talk about. These sources do not cover his religion, leaving the speculation to various other sources that are likely doing guesswork. The best results seem to point to Shinto with the given reasons being it was the party backed religion and one of the majority religions in the region. This isn't particularly convincing to me as this wouldn't be considered strange in Japan, which would lead the shooter to rather target him for political motives. Unless the shooter disguised his motives through the excuse of religious difference, I don't see that Shinto as his actual belief structure. Plus, the sites suggesting this misspell Shinto as "Shito".
This lack of information will lead to a lot of speculation. If Shinzo Abe was involved in secret societies, perhaps the gunman was an initiate that needed to prove allegiance through assassination. I can't say for certain, but assuming religion is the actual factor, this is what I would have to conclude. I cannot find much information about religious conflict or warfare between Shinto and Bhuddism, or other minority religions in Japan. Perhaps they exist, but I can't seem to find the right information about it. I especially can't find the gunman's religious info at the moment.
So, motive is a big mystery. The means of the assassination is this hunk of junk held together with wood and tape. Clearly, this jap didn't quite clear school with the highest of grades, but it seemed to do the job, so you really can't fault the design too much.
""This guy couldn't get traditional ammunition probably, because it's highly regulated," Chipman told USA TODAY. "He had to basically make an explosive. We call it a shaped charge.""
https://news.yahoo.com/homemade-gun-used-assassination-shinzo-210301812.html
Finding even this information was a pain as all mainstream news sources seem to talk about is how this relates to US laws and weapons. The design was a double barrel design to mimic a sawed-off shotgun, and he made his own explosive charge to fire pellet projectiles. It apparently hit his heart on the first shot. Interesting event overall, but it seems that will be the limit of what can be known for a few days until more comes out. I'm still hoping someone will let us know about what religious order was involved, if any.