Mii (Switch) is a Mii in the files of Miitopia (Switch, Demo), with him being the default Mii for the Dark Curse role. However, unlike the other Miis, he is not selectable as a "default" option when initially casting the role. First, he must be replaced with a different Mii. Then, that Mii must be deleted from the Mii Bank. Only then will Mii show up in highlight replays and other cutscenes. His Mii data file can be found in \cmn\storedata\npc_default_mii.sarc and is named Reincarnation.charinfo.
His Mii name in his Mii data file is ななし, which translates to "nameless". His Mii ID is as follows: 2F 42 68 B4 16 FD 45 87 A5 B1 D7 4E DA 0C CF 7D
His Mii data file does not contain any unused Mii data.
Mii (Switch)'s role in Miitopia (the Dark Curse) is described as so:
This is the only time where, in an officially developed and published Nintendo game, the default starter male Mii has appeared in-game through normal means.
Mii (Switch) unfortunately does not appear in any promo art. Below is a screenshot of him in-game as his role in Miitopia (rewatching a cutscene after deleting the previous Mii casted in the Dark Curse role).
This Mii originally appeared on the Switch!
Here's how to recreate them on the Switch:
Names in other languages
Source: Miitopia (Switch, Demo)