Numbers sourced from a three month period ending February 2012 show Android's share has passed 61 percent in the country, growing at an average of 0.1 percent a month.
While iOS's share is also expanding and at a faster rate Apple remains way off challenging Google at the top of the table.
Indeed, iPhone now holds a 34.2 percent share of the market, up 1.3 percent over the course of the three month period equal to a rise of 0.4 percent every month.
Interestingly, despite its solid smartphone share, Apple is only the eighth largest mobile manufacturer in the region - thanks in the main to the prevalence of feature phones.
As such, Sharp is currently top dog in Japan, with a 23.5 percent share, comfortably ahead of Panasonic in second on 13.8 percent and Fujitsu in third on 11.8 percent.
According to comScore Japan VP Daizo Nishitani, however, the balance of power between feature phones and smartphones is currently shifting.
"Smartphones surpassed feature phones as the most acquired device type in February 2012, signaling an important shift in Japan's mobile market," said of the results.
"The rise in smartphone adoption opens the door to tremendous opportunity for publishers and advertisers to expand their reach and increase engagement with key consumer segments through this channel.
"Japanese mobile phone users were already highly engaged with their devices, but with the added functionality and higher levels of mobile media consumption we should expect to see significant changes in behaviour among the Japanese mobile population in 2012."
You can read the results in full over on comScore's website.