I mentioned in a post about how I seem to write Kyuzo as somewhat unwilling with Kambei and Jun-I has some good input on the subject. What do you think about their relationship?
As for unwilling/vicitimish Kyuu, I agree with your assessment that victimish wouldn't be the right word. But still, I don't see her making the first move or aggressively pursuing the relationship, at least not until Kanbei provokes her to the point where she wants 'revenge'. In my interpretation, Kyuzo's 'passivity' is not so much out of shyness or fear, but because s/he's the kind who would rather be the one to do the rejecting than to put himself/herself in a position to be rejected.
She'd probably prefer to keep the situation as "Kanbei wants her more than she wants him." That's probably quite a different theory from your "Kambei has to prove he's worthy to touch her", though I think that reason for her 'reluctance' makes sense too. For all you know, her "frigidity" might be a combination of both reasons and more ;-)
I've noticed that in most of them, Kyuzo appears as somewhat unwilling, almost victimish. Kyuzo and victim don't sound right in the same sentence... Anyway, if Kyuzo really didn't want Kambei, he would end up missing a few limbs. I don't care how good Kambei might be. As I was saying, I tend to see it as more of a test, almost as if Kambei has to prove he's worthy to touch her. Does that mean she'll accept any man who could defeat her? Of course not! It's all a game to them. Although the fact that Kambei is nearly superior in skill seems like an exciting turn on for someone like Kyuzo.
Ah, it makes so much sense in my head.
But we can't always have Kambei being the pursuer, can we? Wouldn't it be interesting for Kyuzo to decide that she wants Kambei and she is going to get him. Maybe then I could portray Kambei as a little more mature/stoic/not so dirty. Even if he is dirty. Kambei being on the run for once. ^_^
And one idea for a lemony scene would have something to do with a blindfold. Not really a bondage scene. Hands would be free, just with a blindfold. Almost like an excercise in trust. I think I'll work on this one.