According to comScore, Microsoft, Google, Apple, RIM or Palm devices rose by 33.5 per cent between September and December 2010.
The firms are therefore able to reach 6.9 per cent of the total mobile audience - just under seven million people.
Apple remains the market leader, comScore said, with iPhone ownership growing 48 per cent since June to reach 3.8 million.
However, the research firm revealed that Google Android-powered devices are growing fastest in popularity, with total ownership rising from 435,000 to 2.2 million over the six-month period.
"Recently, carriers and operating systems have made the push into Japan to introduce smartphones into this sophisticated mobile market," comScore said.
"Many smartphones in Japan have advanced capabilities such as mobile wallet, 1seg TV and waterproof features, all which encourage current feature phone users to switch to smartphone devices."
