There is little arguing over the popularity of Steins;Gate, however Steins;Gate 0 managed to break all past records. According to Mages’ executive director Chiyomaru Shikura the game sold over 100,000 on launch day in Japan.
— 志倉千代丸 (@chiyomaru5pb) December 10, 2015
To put these numbers into perspective the original Steins;Gate sold around 16,000 copies in its first week and an additional 4,000 in its second week. With these recent sales of Steins;Gate 0, the series finally sold over 1 million copies in total.
Steins;Gate 0 is the first true sequel in the series and is available for PlayStation 3, PlayStation 4 and Vita in Japan. We are still awaiting word on a western release.