The overwhelmingly rabid desire for Splatoon 2 in Japan has caused the sequel to sell over 671,000 units in a mere 3 days (excluding digital sales via the Nintendo eShop), easily trumping Breath of the Wild which only managed about 193,000 (a pitiful amount compared to the west).
The information was divulged courtesy of Famitsu, who also reiterated that there are over 1 million Nintendo Switches in Japan – meaning about 67.1% of Switch owners possess the ink-bases sequel (or else non-owners are seriously jumping the gun).
That being said, many may suspect Splatoon 2 only sold as well as it did due to its special bundle which included a Nintendo Switch system alongside the game…