After watching the clip, I agree with some of what has been said before... I also think that Nayuki sounds a bit older than what we're used to, but I believe that that can be worked on.
I also think that Chris Patton's voice of Yuuichi is a bit... light. I personally think that he should use the tone of voice he used as Tomokazu Mikuri in Yumeria.
As for Ayu, I'm not really sold on her voice yet... need to hear more...
