Currently Google Maps is simply moved their satellite imagery to south east about 450m in the area (shown as a red box : N30-50 and E115-152) to loosely adust to Zenrin's Tokyo Datum based Japanese roadmaps it uses.
But the area doesn't cover some part of Japan (esp. Okinawa islands),
covers whole North/South Korea, and part of China and Russia.
Same kind of roadmaps are available even for Okinawa in Google Maps.
Related Blog Entry:
earthhopper: Google マップ / Google ローカル、次は韓国じゃなくて台湾か?