Zoro → Hmm, I'm wondering what you may have in mind for him regarding the dojo? If you think he'd train anyone/have fun beating the stuffing out of someone, you are welcome to Okumura. He is still very rough around the edges with regards to sword skill. At the very least he would be impressed by him -- anything goes really. :x
Hinata → Okumura would also be very impressed with her. Cute, shy girls are of course cool to him -- although he can be a weird, fighty gremlin at first impression too...but if they ever crossed paths, he would try to be friendly.
Haru → Hmm, it's hard to say. If he is the quiet, serious, introspective type, it would probably remind him of his brother, Yukio. I don't think he would really be too put off by it, if they ever met. Okumura might want to go swimming sometime where he works as a lifeguard, who knows!
Riza → He looks scruffy, and has a bad attitude and probably is out to get into trouble! She is welcome to give him a hard time, of course. It is more than likely that he got into a fight, sometime, somewhere. XD
Anything you can think of, that you might like really. I am excited to see them all in game!