There is no doubt that North Korea shot the Japanese police director general, but it was quite a difficult question to answer why they did that.
I assumed that he was shot with an issue related to the Aum cult. At least, it was true that North Korea was related to this cult said to be that they bought a firearm capability from North Korea. They also said to be related to the drug business or they might have been related in terms of the chemical weapon.
Adding to this, North Korea was not necessarily to shoot him from the scratch that they should have negotiated with the police intelligence to halt an investigation toward them.
There was a fact that the No 2 of this cult was stabbed on 23 April 1995, who was in charge of all the illegal operations conducted by this cult. He actually mentioned on TV that he was going to talk everything someday later on until death. He was killed by North Korean in front of TV cameras.
Just in case, this perpetrator clearly mentioned in his book that there was no order from the North Korean government. He lived in Japan with North Korean network related to their government, though there was no proof this stabbing was ordered by them.
In any way, the Aum and North Korea had a relationship and they actually expanded their religion to Russia as well, which is why there are still bases of them in Russia.
It was not just because they were close to Japan, but there were left extremists inside this cult. I am not sure how influential they were, but it appeared as an extension toward Russia and North Korea.
It is pretty much sure that North Korea shot the police director general, but I still had no idea why they did that, though I assumed that the leaders of the police intelligence in those days still remember why North Korea targeted him.