I had a good time with this audio.  I don't think I could ever quite fully accept this cast as the original TARDIS crew - they all sound and feel much to different for that to feel quite right to me - but there's so much to like here it easily overrides something like Ian sounding a little different.  I really liked the authentic casting of Japanese characters as a lot of them worked quite well, even when you could kind of tell this was written by somebody with a British perspective more than a Japanese one.  Still, it's a good story, featuring a lot of interesting characters from the historical Japan setting, having an easy-to-follow plot that was just as easy to enjoy, and most importantly, Ian actually got to behave like a chemist.  It's hard to go wrong in such a situation.