Formerly Yaohan, a chain of Japanese department stores found throughout the United States. (They may be found elsewhere, but I'm not aware of any non-U.S. locations they may have. Most Yaohan-goers I've talked to place the name change as occurring early in 2000.)

A Mitsuwa will typically contain an Asian supermarket, a video rental place*, a few restaurants (the smallest I've seen only had one), and mini-stores selling books, toys, dishes, Sanrio stuff, appliances, and accessories with which to trick out your lowered Honda.

*If you can deal with the lack of subtitles, a great place to get the latest anime series. Ditto buying manga at the bookstores. :)