Coop doesn't work for Japanese sites that are encoded with normal Japanese character sets. Google page rank actually doesn't pick up normal encoded Japanese sites. It's probably the same with other 2 byte languages like Chinese, Korean, & languages in the middle east. This is not the problem of the Coop it's just that Pagerank probably only works if those sites use Unicode. I'm going to recreate the site of my company owner in Unicode & see if there is a difference. The only bad thing is even though the site has many backlinks to it already they are mostly Japanese sites not encoded in Unicode so the pagerank will probaby be low.
That's my point normally Japanese sites aren't using Unicode. They are using Shift JIS. Since they use this Pagerank also can't be determined so it looks as if the site hasn't any backlinks from Google. For example a Japanese site may have 50 backlinks from other Japanese sites using Shift JIS encoding but those backlinks don't affect pagerank or google standings in English.