There is no actual JCAB BMI limitation. It is stated that above 30, however, further tests are to be performed.
http://www.aeromedical.or.jp/manual/manual.htm
(Its all there but in Japanese)
Each airline seems to have their own limit below this. One of the contractors seems to require less than 27.
Haywood>
you be able to say what airline that is? Osaka? So, maybe the Dash-8?
(I lived in Osaka for 6 years and dream of moving back there one day!)