Yeah, that would work. I wouldn't mind Kitaru getting a little beaten up because getting into fights he can win is in character for Kitaru.
Well I think that if Ethan just starts to analyze Kitaru's behavior then Kitaru will eventually snap. The tricky thing would be pushing his buttons to make him want to battle Ethan instead of just beat him up. I would say that Kitrau's honor should be used as leverage but if you have any better ideas then just go with them.
One idea could be have the fight first then meet Ethan who notes that Kitaru has been in a fight and has bruises consitant with fighting a lot (or something like that any way). It being suggested that Kitaru is a fighter he would likely battle for his honor despite the fact he gets into fights all the time XD