Ryng on 03 June 2015
According to Media Create, the week ending 23 May 2015 (24 May in Japan) Mario Kart 8 pass 1M mark, with 1,006,719 unit sold.
05./06. [WIU] Mario Kart 8 # (Nintendo) {2014.05.29} (¥6.156) - 11.654 / 1.006.719
Retail only.
That's very amazing week for WU between Mario Kart 8 and Splatoon. 
