That is really cool. I don't know if you have tried yet, but i thought I would encourage you to write the contact address. An astonishing number of Japanese people are proficient in English. I have contacted a "Japanese only" site in the past, on the off chance they spoke English, and was given a response by someone who had English skills well beyond my own.
![:-)](./images/smilies/icon_smile.gif)
You never know.
As for LD audience size in Japan... I don't know how it is for games, but for movies it is still pretty hardcore. If I recall my news correctly, Japan was the last country to have full size LDs in retail outlets. And they held on YEARS after they were gone here.