This is a common concern. The Mii Maker application is copyrighted by Nintendo. However, the legality of downloading it for use with Citra falls into a gray area:
If you are a fan of Nintendo 3DS emulation, you’ve likely heard of —the leading open-source emulator that allows you to play classic 3DS titles on your PC, Android device, or Mac. However, many users run into a frustrating roadblock: games like Tomodachi Life , Miitopia , Mario Kart 7 , and Find Mii require a Mii to function properly. Without a Mii, these games may crash, display error messages, or refuse to progress past the title screen. citra mii maker download
Deep within the folders of a dusty PC, a user named Alex stared at a blank screen in Tomodachi Life This is a common concern