The game in future builds will have two nurses: the official nurse and the substitute nurse rival. The official nurse will be taking a vacation when the rival's week comes. A new official nurse will be generated if the previous one dies. All the nurses will be minor NPC faculty members.
Once she is fully implemented, the player will need to sneak past her to access the tranquilizer and the syringe. YandereDev has stated that certain medicines will be kept in a locked container hiding somewhere in the office in the future. It can only be opened with a key, which the nurse will hide in a different spot each week.
She has fair skin and light pink-colored hair and purple eyes. She wears a short-sleeved white nurse uniform with a low collar and a nurse's cap. She also wears light pink stockings with a white garter belt.
She is outlined in red in Yandere Vision.
"Muja is a young nurse who desires nothing more than to take care of other people...although she usually ends up causing more problems than she solves due to her air-headed and klutzy nature.
Muja will be serving as a substitute for the school's usual nurse, who isn't available during the sixth week of gameplay. She will become fond of Senpai very quickly, during a point in time when he definitely needs someone taking care of his health.
Her intelligence is not her strongest point, but she is a very sweet and caring person, and it's very easy to see how any schoolboy might develop a crush on her - including Senpai..."
Unlike Mida Rana, the subsitute teacher, Muja is meant to be "pure" and "innocent". While she will also make frequent sexual innuendos, they will be unintentional on her part. She is probably the only Faculty member who is incapable of self-defense.
In the final game, Senpai will become sick for the one week while Muja is at the school. He will visit her once every day. Senpai is attracted to sexy and hot nurses, so their relationship might grow as a result of these interactions.
If she entered a relationship with Senpai, he'd pursue a career in the healthcare industry.
- Muja will disappear when her week is over, even if she is eliminated peacefully.
- YandereDev has stated that the substitute nurse is not a rival who can catch a knife.
- In the final game, when a student is poisoned or drowned, witnesses might run for her instead of the teachers.
- Her name is derived from "無邪気" (mujaki) which translates to "innocent" and "simple minded". "な" (na) is an adjective-modifier.
- YandereDev has considered the idea of Muja attending Akademi when she was younger, and always having the fantasy of confessing her love under the cherry tree, but never finding the right person. She would compensate for this in a childish manner by confessing to Senpai under the cherry tree. 
- She won't have a reputation stat, but will instead have a 'job performance' stat, which will be lowered in ways other than gossip.
- YandereDev does not believe she is acquainted with Mida Rana.
- YandereDev has stated that she may be the only faculty member who does not have self-defense training.
- Muja's reaction to murder would be to warn others in the Faculty Room, she may go the wrong way at first.
|“||Oh, my! Your face is turning red! Do you have a fever?! Come see me any time! I'm always happy to take care of you...||”|
— Muja in "Yandere Simulator Rival Introduction Video" 
|“||Oh, my! Your heart is beating so fast! Are you getting sick? I'll always be there for you Senpai. I'd be happy to take care of you for the rest of your life.||”|
— Alternate Muja line for the "Rival Introduction Video".
|“||I don't know what you're trying to do, but if it's supposed to be a joke, it's not funny.||”|
— Muja when Yandere-chan fails to steal her keys.
|“||EEK! WATCH OUT! ...owwwww...I'm sorry, I got you right on the head, didn't I? Here, let me see...oh, no! I gave you a bruise! I'm so sorry! Sorrysorrysorrysorrysorry! ...huh? What's this flower doing on the ground?||”|
— Hypothetical dialogue of Muja reacting to someone giving her a flower.