Between April and June of 2012 4,000 mobile phone or smartphone users aged 13 or above completed a survey, but information on how the sample was generated, more detailed demographics, etc was omitted. Furthermore, the data has been post-processed, I think, to reflect the overall demographics of Japan, so the numbers below can be treated as statistics rather than survey results.
Note that in Japan around 102,700,000 people aged 13 or above have mobile devices.
If we further note that 23.5% of the population own smartphones and Apple is 32.3% of that, in S1 that would put Apple at 7.6%, just behind Sony. Unfortunately, we cannot do a similar simple calculation to estimate Samsung’s market share in Japan.
S1: Mobile device share by manufacturer.
Sharp 22.6% Panasonic 13.6% Fujitsu 11.8% NEC 8.9% Sony 7.9% Other 35.2%
S2: Smartphone operating system share.
Google Android 64.1% Apple iOS 32.3% Microsoft Windows Mobile 3.2% Other 0.4%