Nintendo has sold more than 2.8 million copies of Mario Kart 8 since the game launched at the end of May.
That means nearly a half of all Wii U owners (of which there are believed to be about 6.6 million) have purchased a copy of the game, representing a significantly high attach rate.
However, the latest entry in Nintendo's money-spinning racing series didn't manage to considerably broaden the system's appeal to new audiences.
About 510,000 Wii U consoles were sold during the three months ending in June, which represents a year-on-year increase, though not enough to make a meaningful change to lifetime system sales.
Wii U sales now stand at 6.68 million units. Nintendo plans to ship several major games for the console this year, including Smash Bros, Bayonetta 2 and Hyrule Warrriors.
For the first quarter of the current financial year, Nintendo lost £57.2 million.