You might try a commercial carrier such as Hanshin or Hankyu. I use both on a regular basis in my business. Yes, there are duties -- this type of carrier will handle duties and facilitate clearing customs in Japan. Shipment should most certainly be by air -- both in the interest of time and the condition of the product.
I've used a variety of Japanese equipment(non-audio)here in the U.S. and vice versa with the use of an adapter. There are product specific adapters available in Japan. I doubt that doing this is a good thing with audio, so your buyer is either going to have the unit modified or has different plans/options. Good luck.
I've used a variety of Japanese equipment(non-audio)here in the U.S. and vice versa with the use of an adapter. There are product specific adapters available in Japan. I doubt that doing this is a good thing with audio, so your buyer is either going to have the unit modified or has different plans/options. Good luck.