Russia Sushi is a restaurant owned by Denis. Simon Brezhnev is Denis' old friend and business partner, helping to attract customers by handing out flyers and waving signs. Many characters often go to Russia Sushi to eat and hold the place in high regard, even though its sushi is considered unorthodox.
In episode 8, when Shinra and Celty go for dinner, the restaurant is out of fish, and they are served "special" plates of sushi for a "good price." The ingredients "shouldn't be made into sushi," according to Shinra.