Despite its tech-savvy culture, Japan has for years lagged behind the West in its adoption of smartphones. However, due to the shift from feature phones to iPhones and Android handsets in the last year, app analytics outfit App Annie now concludes that Japan leads the world in app revenue — and the culprit is an explosion in mobile gaming. Smartphone sales exploded in Japan from 28% to 42% According to The Wall Street Journal, Japan bested the US in app revenue this year by 10 percent.