We found a Japanese restaurant that’s not too bad. I think the name is Tsukishima. To get there take the Metro to the High Tech Zone, go out entrance A, walk about 50 meters straight ahead, take your first left after the Tasty Restaurant, then the next left, and it’s on the left about 3 restaurants down. The phone number is 028-85255829 if you want better directions. The speak good Japanese, but their English is so-so.
Oh, they have a pretty good selection of sake.