226 incident is not a terror....
they were believer of state Socialism February 26 Incident - Wikipedia
after this result, The tousei-ha gained power oppositely in Japan.
I wouldn't consider it terrorism, necessarily, myself. It was politically motivated and it had specific political targets. Terrorism is usually an attack on civilian populations with no strategic benefit beyond sowing fear.
In addition, this is dealing with incidents during the years leading up to the Pacific War, and those were mostly at the hands of ultra-nationalist right-wingers and militarists.