So I got a little curious about the Switch's software sales in Japan and I looked back at Nintendo's Supplementary Material pages all the way back to the Switch's launch. Now keep in mind, they only post games that have sold over 1 million units in each Fiscal Year, so this list and data is incomplete, but this is what I have gathered.
Switch Games Japanese Sales:
1. Animal Crossing: New Horizons - 11.64m
2. Mario Kart 8 Deluxe - 8.46m
3. Pokemon Scarlett/Violet - 8.19m
4. Smash Smash Bros. Ultimate - 7.57m
5. Splatoon 3 - 7.09m
6. Pokemon Sword/Shield - 5.64m
7. Splatoon 2 - 5.11m
8. Ring Fit Adventure - 4.09m
9. Breath of the Wild - 3.87m
10. Pokemon BD/SP - 3.85m
11. Tears of the Kingdom - 3.71m
12. Pokemon Legends: Arceus - 3.64m
13. Super Mario Odyssey - 3.32m
14. Super Mario Party - 3.17m
15. Super Mario Bros. Wonder - 2.68m
16. Nintendo Switch Sports - 2.37m
17. Mario Party Superstars - 2.18m
18. Pokemon Let's Go - 2.18m
19. Pikmin 4 - 1.87m
20. Kirby and the Forgotten Land - 1.84m
21. New Super Mario Bros. U Deluxe - 1.82m
22. Super Mario 3D World + Bowser's Fury - 1.82m
23. Luigi's Mansion 3 - 1.46m
24. Super Mario Maker 2 - 1.43m
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