Launched in 1997 by Julian Metcalfe, the founder of Pret a Manager, the brand currently has 40 stores in London and two restaurants - in Chelsea and Notting Hill.
Itsu is now due to open its first store outside the capital in Oxford and in an interview with The Sunday Telegraph, Metcalfe said he would eventually look for an investor to help bank-roll the expansion.
"We have money for 30 more stores at the moment," he said. "The 30 will keep us busy for a bit. Then we will have to think about how we do it."
Metcalfe currently owns the majority of the company, with a minority stake shared between Clive Schlee, the boss of Pret; Gerard Loughran, the chief executive of Itsu; and Robin Wright.
Pret was sold by Metcalf for £345m in 2008 to Bridgepoint, the private equity company.
Itsu offers a menu of salads, miso soups, sushi, noodle and rice dishes focused on "skinny but delicious" food. The company currently generates revenues of £55m per annum.