The most popular methods for Japanese to make purchases on the on the net often do not include cards. Nihonjin are conservative with cc use.
You may wish to contact this company,
https://www.unionbank.com/personal-b.../eng/index.jsp -- they can give you a feel for the landscape.
They are the American branch of Japanese conglomerate Mitsubishi Bank. In a recent poll of Americans using banks, Union Bank received the highest rating in an industry with lower overall ratings than US Gov/Congress and Wall Street. lol.
We work with many Japanese adult companies providing a wide range of services from DVD and blu-ray sales to translation work and membership site promotions.
Send me a PM if we may be of assistance.
JAI