The included update (e.g., v1.2.0 or later) brings:
Previously, co-op meant taking turns. Now, two players can boxing side-by-side on the same screen using two sets of Joy-Cons. This adds a competitive "Perfect Sync" bonus if you match rhythms. Fit Boxing 3 Your Personal Trainer -NSP--Update...
The reason you need the update file is for the Season 1 DLC Pass. Without the v1.2.0 update, the Switch will not recognize the DLC NSPs. The paid DLC includes: The included update (e
Cost: $14.99 USD for the Season Pass. Individual trainers are $5.99. The reason you need the update file is
Disclaimer: This article does not endorse piracy. The following is for educational understanding of file formats.
Warning: Installing the update (v1.2.0) is mandatory for the DLC unlockers. The DLC trainers (see below) will not work on the base game (v1.0.0).