Japan has a lot of social game platforms. Japan has much social game platforms. Therefore I made a Japanese main social game platform list.
mixi(PC/Mobile)
History of Japanese open platform began in mixi(from 2009 summer). However, mixi loses in Mobage and GREE now.
Mobage(PC/Mobile)
They are the second open platforms in Japan. They were only mobile, but they cooperated with Yahoo!Japan later and opened
Yahoo! Mobage(for PC).
GREE(Mobile)
They are late departure, but are a platform making money most now. They offer a social game only in mobile.
Ameba(Mobile)
Ameba is a CyberAgent's social community. Ameblo(Blog) and AmebaPigg(Virtual World) are famous, but they provide a lot of games for mobile in conjunction with them.
Colopl(Mobile)
Colopl is known as operator of mobile geolocation social game. However, they are platforms specialized in geolocation game with it.
NicoNico Douga(PC)
NicoNico Douga is Japanese popular video sharing site. They open platform "NicoNico application " which can play a social game while watching video.
Hangame(PC/Mobile)
Hangame was well-established online game portal site. However, they make efforts in a social game now.
entag!(Mobile)
They are the mobile social game platform which just opened on January 11. They assume mobile SNS "logtomo" which started in 2007 and renewed it on starting a social game site with a smartphone.
DMM.com(Mobile)
They are japanese PPV sites, but are known as porn video site mainly. They started a social game platform for mobile experimentally. Their characteristic is providing a porno social game. Hentai eroge and social game, this is the strongest combination! :)
Japan has many platforms besides these. Those big characteristics is almost of "for future phone". And everybody globalization and cross platform are behind.