Do not install the update first.
If you run into any issues, double-check your Sigpatches and ensure you are installing the files in the correct order (Base -> Update). Now, go save the kingdom! monster boy and the cursed kingdom nspupdate work
Optimizing Monster Boy and the Cursed Kingdom: NSP Updates and Performance Guide Do not install the update first
If you are still using the older :
The NSP update for Monster Boy and the Cursed Kingdom is stable. It does not introduce new Digital Rights Management (DRM) measures beyond standard Nintendo licensing checks, which are bypassed by standard CFW patches. The gameplay experience is significantly improved by the patch due to the removal of soft-lock scenarios present in the initial release. Optimizing Monster Boy and the Cursed Kingdom: NSP
Critical fixes for Haunted Mansion ghost, lootmaster, and quest progression. v1.0.2 (November 2018): Japanese language formatting fixes. v1.0.1 (October 2018): Visual and framerate improvements.