The smart-phone category is comprised by their definition as "mobile devices running iOs, Android, MS Windows Phone, RIM's OS, and Symbian S60" (which is not offered in Japan).
I am not clear in which functions "advanced function phones" differ from smart phones, as all functions available on smart phones are seemingly present in these advanced function phones.
Understanding how smart phones are defined it is no wonder that iOs and Android make up more than 90% of the Japanese smart phone market.