This isn't really crit, but that's simply because I think you have no reason to worry over Kuro's voice. This is just my opinion, but I think you're doing great - from what I've seen, you balance it perfectly between his grumpy, straightforward character and with the more mature feelings he has gained up until the canonpoint he's from. I can imagine how hard keeping that balance must be, and frankly, I'm really impressed how well you're doing. The only little piece of crit I can think of is that maybe he's a little too somber sometimes? Then again, considering his canonpoint and all the shenanigans that have been going on with his CR, I think it's justified, so. Tl;dr I think you're doing perfectly with him and have no reason to worry whatsoever.
I can say the same for Hokuto; it's a delight to see you play her, she's absolutely amazing. So, no need to worry about that, either.