Berkut is called Berkut-sama by an Eurotean man. But why? Everyone (except Klaus) calling Taki Taki-sama makes sense since they live in a Japan-like country with Japanese names and everything, but isn't where Berkut comes from a place more like Germany with all the Gratuitous German? Shouldn't he be called Herr Berkut (even Lord Berkut or anything not so uniquely Japanese) or something like that? Even if Berkut is not from the same country as Klaus (the geography of this world can be a little confusing sometimes), he sure isn't from Taki's land.
It appears that Taki never properly explained to Klaus just what their relationship would be once Taki became the Maiden Rose. Why? He had to know this would be both baffling and hurtful to Klaus. They went from being lovers to Klaus not being allowed to touch him. Repeatedly smacking somebody's hand away isn't explaining to them that you have to be a symbol of purity. I feel like a lot of the heartache between the two of them could've been avoided if Klaus knew that becoming Taki's knight meant that he had nothing. Not just having no more homeland or family, but not being able to be with the man he loved that he threw his whole life away for.
I suspect that Taki didn't explain everything to Klaus for because he was afraid that if Klaus knew what it REALLY meant to be his knight he would leave him. Klaus is not only his lover but the only person that doesn't care about Taki expressing his feelings. Him holding back information from Klaus is probable.