Lovers
It's a poorly kept secret that Kazuki humors his protectors. For all their strength, their emotions are fragile things, and Kazuki strives to keep them happy. He has learned to bear their reverance with grace, though he does not think himself the prince they so adore. He is a man, like any other, and he has not earned their devotion.
Still, he loves them. Loves Juubei's silence, his ability to believe--absolutely--in something the way Kazuki never can. He loves Toshiki's brash nature, the firey temperment that hides a wounded soul. He loves them and so accepts the roles they have chosen. They, the protectors, he, their reveared lord.
But on cold nights in Mugenjou, it's not their reverence he cherishes, curled between them safe and warm and adored, it's the serenity they give him by virtue of their love.