Using a save with illegal moves (e.g., Pikachu with Hyperspace Fury ) will crash Yuzu or corrupt the file. Stick to "legal" saves.
In the context of the emulator, "Extra Quality" save files for Pokémon Sword Pokemon Sword Save File Yuzu Extra Quality
To achieve an "extra quality" experience for Pokémon Sword Yuzu emulator Using a save with illegal moves (e