Japanese game developer Cygames announced that they got more than 20 million registered users.
Of course, J-Style card social game "Rage of Bahamut" to have pulled it. Cygames was established as a subsidiary of CyberAgent in May, 2011. And they released Rage of Bahamut in Mobage in September, 2011, and it made a hit immediately. It is still ranked the high rank of Mobage's popularity ranking. And they run not only its Japanese ver. but also English ver., Korean ver. and Chinese ver. The totals of Rage of Bahamut users of the world are more than 10 million. In other words, half of 20 million registered users which they have are Rage of Bahamut users.
They cite cool artwork as the factor of the hit of Rage of Bahamut.