According to a post at Wandering Aramean, ANA (All Nippon Airways) will be adding free wi-fi to its aircraft used for domestic Japan flights. The provider is Panasonic.
Japan Airlines already provides free wi-fi for domestic service. Their provider is Gogo.
ANA will also add USB power ports an embedded entertainment screens on many of its new and existing aircraft. This is in contrast to some American carriers, who are deleting screens (and reducing costs and weight) based upon the assumption that passengers will bring their own devices onboard.