A new and almost the only one, if we put aside sushi counters in two of the local Euroross supermarkets and the Greenwich cafe that used to advertise sushi, was noticed in Kandalaksha. It is on the side of the pedestrian overpass opposite to (south from) the train sation. The address is Komsomolskaya 32A, and their VK page is https://new.vk.com/bentokanda.
Yet to be visited in person.