Goujun says 'na' a lot at the end of sentences, as does Kenren. Blunt in language more than formal. It's Kenren who says he's a strait-laced killjoy, basically, and that's how loose-laced Kenren registers him. But we never see Goujun talking strait-laced, so presumably I should unLatinize his language, at least when he's talking to juniors.
Goujun's called a toushin too- comes from an ichizoku of toushin, K says- which suggests interesting things. The toushin *prince* (taishi) is the designated slaughterer in Heaven, but what do we make of a toushin ichizoku? Ichizoku IME is larger than a family and a little smaller than a race: clan is about the size of it. But if all the royal dragons are toushin can they kill? Evidently not since the toushin taishi is called the *only* person allowed to kill in Heaven: but are dragons considered part of Heaven? Given the looseness of Japanese definitions in general, that are based more on (emotional) common 'sense' than logical scrupulousness, maybe not. 'Everyone knows' that Heaven means the kami and not the foreign dragons- that's just common sense. (Just as everyone once knew, and occasionally still does, that Canadians are white by definition. Even the occasional Asian-descended friend will say quite casually that their brother is going out with a Canadian girl. A matter of definition.)
The other suggestive bit is Kenren telling Goujun 'Be careful that that 'outstanding' pet dog of yours doesn't bite you some day.' That suggests to me that Goujun may have been fundamentally mistaken about Tenpou all along- which is exactly what the last installments suggest. Goujun thinks of Tenpou as an excellent soldier (that's canon) who- what? shares his own views? is completely loyal to him? is beyond suspicion? Somehow the extreme eccentricity of Tenpou's habitual behaviour doesn't translate in Goujun's mind as dangerous individualism. Goujun evidently has no doubts about Tenpou at all: he never thinks that Tenpou could ever be against him. But interestingly, Kenren /does/. I get a feel of 'I know something you don't know' in Kenren's taunt there.
Yaoistically that could be jealousy: Tenpou has feelings for Goujun- loyalty, whatever- that Kenren dislikes because he himself doesn't like Goujun. Kenren feels no such jealousy for Konzen... well, not that I can see. So I'm less inclined to ascribe the remark to jealousy than to some attitude towards Goujun that Tenpou has conveyed to Kenren but concealed from his superior officer. And the question is what? and perhaps more, why?