AHC/WI: Terrorism/Political instability in Japan (Shōwa era, Heisei era and Reiwa era)

The challenge is to make this development happen after WW2

You may choose any PoD as back in the Meiji era
I know of one POD to accomplish this, at least in the post-WWII era that is (if you're going for more terrorism than OTL's): simply by having North Korea win the Korean War, which prompts the US into having a more strict occupation of Japan and yet allowing Japan to rearm itself, which dents the economic recovery for the country in the coming decades. This in turn, leads to Japan becoming somewhat more authoritarian than OTL's, especially with Kishi on board; and of which leads to stronger Communist terrorist organizations being motivated by the "imperialistic" actions of both Japan and the USA (the former of which might go on to send troops overseas to help its anti-communist allies).