Since when does Harmonia have Imperial Knights? This also isn't mentioned in any characters profile for Nash, but they do mention that he used to be a Temple Guard and the only information on Harmonias army I can find is that there's the Temple Guards, Central Army, Regional Army and finally the Southern Fringe Defense Force.おれはいつだって無力だ。
近衛騎士団で習った剣術も、
When did I become so powerless?
The swordsmanship I learned in the Imperial Knights
I suppose you could go with Imperial Guards but I can't see anything that's mistakable for Temple.