My website has a tripreport on Japan. Been to Tokyo Narita and Haneda, Nagoya and Osaka Itami and Kansai.
Itami had one YS11 flight when I was there in November. I am not sure if you still can see YS11's there, as JAC
is operating the new Dash8-400 to Itami.
Haneda has some YS11 of the Japanese Flightinspection I believe.
Nagoya has a military airbase on the other side of the airport. When you are lucky you might see a military YS11.
My website is at http://www.spottersunited.com
Select the Trip reports section.