According to the latest Japanese sales numbers 499k physical copies of the game have been sold since October, making it the fastest-selling entry in the franchise in Japan.
It’s on its way to be the best-selling entry of the franchise as well, with Pikmin 2 having sold approximately 480k units and Pikmin over 507k respectively in Japan. Note that the current sales numbers are only for the physical copies, so with digital sales that number may have already been surpassed.

Source: GoNintendo