Fire Emblem Fates is off to a great start.
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I guess people still bought the game anyway and I guess having Corrin in Smash also helped.
With more than 300,000 units sold between all versions of the Fire Emblem Fates game during its launch weekend, the Nintendo 3DS strategy RPG earns a place in the record books as the fastest-selling game in the history of the long-running, critically acclaimed franchise in the United States. The game sold more than five times as many units as 2013’s Fire Emblem Awakening, the previous record holder in the United States, during its first three days of availability.
Source
I guess people still bought the game anyway and I guess having Corrin in Smash also helped.