You are like 20 years too early, Taisho Era takes place at the same time as WWI
Nah, Mao happens after 1923 (The Kanto earthquake was a plot point a while ago if you remember). There were plenty of fascist around at this time, they just didn't had usurped absolute power yet.
In Japan this was around the start of the Goverment by Assasination era, where the civil goverment lost all control to the military because anyone vaguely liberal got murdered.
Which is, of course,
Habuki and their cronies whole deal. They are political assasins that murder liberals to help the future fascist takeover.
So yes, they are, unambiguously, 100%, without doubt, genuine nazis.