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.

According to The Wall Street Journal, Japan bested the US in app revenue this year by 10 percent. That's up from spending 40 percent less than the US last year. The reasons for this shift are two fold: Smartphone penetration in Japan has boomed from 28 percent last year to 42 percent in 2013, putting it apace the States' 44 percent. That led to an incredible increase in apps being sold, and games apps are leading the way by a wide margin. App Annie lists game publishers like GungHo Online and Sega as driving sales. In addition, Google Play sales skyrocketed in the country — far more than any other place in the world — putting it on equal footing as App Store sales.

App Annie expects smartphone sales in Japan to continue growing into 2014, potentially reaching more than 60 percent. It'll be interesting to see how app makers respond, as Japan becomes an increasingly profitable marketplace.

Update: A previous version of this post suggested that Android's footprint in Japan was much larger than Apple's. That was inaccurate and has been removed.