Tessa's fascination with Mio and Quill is based on how Mio, Quill, and Tessa are all names of pets owned by the game's developers.
Michela Laws reprises her role as Ayano now that the voice acting is in the game.
Nutaku was exclusive to the NSFW version hosted on Nutaku, until version 0.120.
Morgan Long has confirmed that Mio is a self-insert of herself. She also uses her natural speaking voice to voice Mio.
Around the same time as multiple developers were removing Yandere Simulator content in response to the grooming allegations the game's developer YandereDev faced, the character Ayano was replaced by an original character named Ayeka.