Tomoko Namba carries the tools of her trade with her. One of Japan's most successful entrepreneurs - and one of the few women at the top levels of business in the country - she has not one but two white mobile phones, as well as an iPhone, neatly enclosed in a white leather sleeve.
The 640 employees of her company, DeNA, run Japan's most popular social networking site for mobile phones. Called Mobagetown - derived from "mobile game town" - it has signed up more than 14m users, a 10th of the population. Last year, the company made a net profit of Y8bn ($84m, €60m, £51m) and Ms Namba's 15 per cent stake has a market value of Y22.6bn.
