He trialled the venture – and the Regent Street venue – as a pop-up in the run-up to Christmas, generating enough interest to raise £55,000 from more than 200 backers.
Koj, which opens to coincide with Cheltenham Gold Cup week, will serve a range of informal Japanese cooking styles – but not sushi. At lunchtime, ramen, hirata buns and Hawaiian-fusion poké dishes will be available for take-away.
In the evening, skewers and buns will be served with Japanese cocktails in the first-floor bar, alongside a range of grazing dishes and daily specials, including his KFC (Koji fried chicken), in the dining room with open kitchen. In the longer term, there are plans for more formal dining and a karaoke bar on the second floor.
British-born with a Japanese father, Kojima grew up in London eating Japanese food at home. He has a degree in classics from Oxford and spent 10 years as a banker before he entering MasterChef five years ago – an experience that prompted a career change.
He started out working as a private chef, teacher and food-writer, and prepared himself for running a restaurant by undertaking stages at some of the best professional kitchens in the country, including Le Gavroche, Dinner by Heston Blumenthal and Restaurant Gordon Ramsay.