It looks like Japan loves to play Mario Kart on the go.
Source
With how while a port of 8 is doing you kind of question why Nintendo would want to work on Mario Kart 9 so soon even though I'm sure it would sell almost double then what Deluxe is at right now.
Go Nintendo wrote:There's been a lot of sales milestones for Switch games in Japan, but I find this one super impressive. Mario Kart 8 Deluxe has just broken a million units sold, hitting 1,045,438 units with this week's sales data. That figure doesn't even include digital sales. This number impresses me because we're talking about a slightly updated version of Mario Kart 8, which didn't release all that long ago! Goes to show how little love the Wii U got.
Source
With how while a port of 8 is doing you kind of question why Nintendo would want to work on Mario Kart 9 so soon even though I'm sure it would sell almost double then what Deluxe is at right now.