I recently came across the Japanese proverb commonly translated into English, "Envy is the companion of honor." This formulation was so alien to my American brain I had to take some time to research and think about it. It seems to be commonly connected to the idea "The nail that sticks up gets hammered down," which I understand better: it means you'd better know your place and be a team player. Very Confucian.
So this is my conjecture and correct me if I'm wrong, but this proverb seems to boil down to this: If you are really going to serve with honor, that necessitates subordinating your own ambitions to the person you serve, and that means you will always have to feel envy. They will always have attainments and privileges you cannot pursue because it would violate your role as a subordinate.
My first thought, of course, was "Wow, that says a lot about Naoe!" It's actually a wonderful articulation of centuries of push and pull in his life. And it frames his devotion to Kagetora as genuinely honorable, which I think, in many ways, is accurate.
This is the first time i read about such a proverb and i think it's beautiful. It does apply a lot to naoe's character. His loyalty and envy walked hand in hand, his honor as a retainer of kagetora but also his honor as a man with natural ambitions always clashed together. I find it beautiful that in the end and after they worked on their relationship none of them had to succumb to the other, but they both were on equal foot with no grudges or resentment.
You make a great point that the end up explicitly on a much more equal relationship. For me, from a Western POV, that reads as a turn that kind of reflects Western, more than Confucian, values. But I guess it's also just more modern, which is appropriate. And I wonder, too, if there's a Buddhist context of moving past appearances and "impermanent" roles.