The group has secured the former Subway unit on Charing Cross Road for what will be its tenth UK opening.
It will offer customisable dishes based around sushi and poke, designed to eat on the move, when it launches this spring.
Diners will be able to build their own lunch boxes from a selection of dishes prepared on-site, with a base of rice, noodles or salad.
Michael Macpherson, of Cedar Dean Commercial – which acted on behalf of the sites' previous occupier – says: “Operators are increasingly seeing a benefit to grab and go concepts and we expect to see a rise in restaurants with a QSR model.”
Sushimania has four sites in London, and one each in Brighton, Cambridge, Oxford, Nottingham and Reading.
It also offers delivery from its restaurants through Just Eat and Deliveroo.