The inevitable has happened – Nintendo Switch has overtaken the Wii U in terms of lifetime sales in Japan.
Between December 2012 to December 2017, the Wii U sold a measly 3.3 million units. It would have been lower if not for the huge appeal and success of Splatoon. As of March 3 to December 24, 2017, 3.3 million Nintendo Switch consoles have been sold in Japan.
In other words the Switch has overtaken Wii U in less than a year. It took 5 years for the Wii U to sell 3.3 million units.