i'm a regular customer of AOI. I've personally never gone there for extensions, only for cut & color, but i wouldn't underestimate their ability to do extensions as Japanese people have a knack for detail and perfection. Granted the only downside is that none of the staff speak perfect English so communication could be hit or miss. I suggest you call them in advance to book a consultion with someone who speaks the best English and go on from there. Perhaps ask them to do a "sample" extension on your hair to see if you like it or not, and they shouldn't have a problem doing that.

Also everytime i go there, i ALWAYS have pictures with me, both of what I want, and what I DON'T want. It really helps them get a good idea of how you want to look.