Good day to all Pilots,sit down and have a tea. I'm here to answer all your questions regarding the Kempeitais business. But since I am not very often in this system, I cannot promise to answer your questions the same day.
Signed: Kempeitai Shogun, Katsumoto Kumo
Regarding the Shogun title thing, I suppose he could use it as an alias, while his title is something more in line with the lore.
General Katsumoto Kumo, "the Kenpei Shogun".
Using it as a self proclaimed title would amount to that, as the significance of the name on the lore prevents the recognition of more than one. It's a Supreme Commander rank.
Other than that, I believe the kenpeitai would be suitable for a translated army hierarchy, or a secret agency ranking.
Tl:Dr you can keep the Shogun moniker informally.
So can use it still in my name KPT|Sho-Katsumoto.Kumo?
Precedent indicated that was the prefix of the Shosa rank in the imperial naval forces and 343 groups. But sure, you can use it as such.