|Strength||Fights back; Strength unknown|
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.
A placeholder nurse resembling Muja currently resides in the Infirmary at all times. Her AI is incomplete and will remain so for several months, so it is not possible to interact with her yet. For that reason, Info-chan will not recognize pictures of her.
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 eyes and hair. 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. As she presumably has a Heroic persona, she will be able to fight back if attacked, but it is unknown how strong she will be.
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 may come up with a story related reason for Muja to stay, after her week is over.
- The nurse was implemented in the April 2nd, 2015 Build. She was given an updated appearance in the July 24th, 2016 Build.
- YandereDev has stated that the substitute nurse is not a rival who can catch a knife.
- The placeholder nurse is unaffected by any Easter Egg or the Demonic Ritual.
- 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.
|“||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" 
|“||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.