As of the March 6th, 2018 Build, there are currently twelve personas that are fully implemented in Yandere Simulator: Loner, Heroic, Teacher's Pet, Spiteful, Coward, Social Butterfly, Violent, Strict, Lovestruck, Dangerous, Phone Addict, and Fragile. YandereDev has confirmed that there will be more personalities. However, more personas would require more animations and having a larger number of students.
The Sleuth persona is planned, but is not in the game yet.
Loners, Teacher's Pets, Social Butterflies, and Heroes will act hostile towards Yandere-chan after realizing she is connected to murder. They will spread rumors about her true nature and will damage her reputation by 10 points each day until they are killed. The Delinquents will also be hostile towards her upon realizing she is connected to murder, but instead of spreading rumors, they will continuously chase her until they put her into a coma. The Coward persona will have less hostile actions and will not harm Yandere-chan's reputation. The Phone Addict persona will take a picture of her committing murder and text it to the police. The Spiteful persona will not harm Yandere-chan's reputation if they hate the person she kills.
Students with different personas will react differently when the player attempts to take a picture of them. If Yandere-chan is in the Photography Club, they will not react.
- Main Article: Coward
This persona was implemented as of the February 1st, 2016 Build. Cowardly students will become terrified of Yandere-chan and will start begging her to spare their life in exchange for their silence. Cowards will cover their face if Yandere-chan attempts to take a picture of them.
- Main Article: Dangerous
All members of the Student Council have this persona. They will push Yandere-chan away if she gets too close. If she approaches a Student Council member and attempts to attack them or gets too close to them five times, they will spray her with pepper spray. If they see Yandere-chan murder anyone, they will run up to her, spray her with pepper spray, then proceed to restrain her, resulting in expulsion. If they discover a corpse, they will report it to a teacher before guarding it. Dangerous students will not react to having their picture taken.
- Main Article: Devoted
- Main Article: Fragile
Fragile students will become terrified of Yandere-chan and will start begging her to spare their lives in exchange for their silence. Fragile students will cover their face if Yandere-chan attempts to take a picture of them. Fragile students can also be used to eliminate other students.
Friendly But Strict
Currently, the only person to have this persona is Kyoshi Taiso. The Friendly But Strict adult will act the same as a teacher and can restrain Yandere-chan. However, Teacher's Pets will not go to them to report a corpse or murder. A Friendly But Strict adult will tilt their head and smile if Yandere-chan tries to take a picture of them.
- Main Article: Heroic
If a Heroic character spots Yandere-chan murdering a student, they chase after her and will trigger a struggle mini-game when they catch her. The player must complete the mini-game successfully to defeat them. Each NPC has different levels of self-defense, which determines the difficulty of the mini-game. Heroes will give Yandere-chan a suspicious look if she tries to take a picture of them.
- Main Article: Loner
Loners will run out of school grounds to call the police if they witness murder. They will sit apart from other students, making it easier to kill them. Loners also cover their face if Yandere-chan attempts to take a picture of them.
- Main Article: Lovestruck
Nearly all rivals will have this persona; however, Muja Kina, Osoro Shidesu, Oka Ruto, and Mida Rana may be an exception to this rule. If a rival with this persona sees Yandere-chan commit murder, they will run to Senpai and tell him Yandere-chan was responsible, which will cause an instant Game Over.
If a rival is eliminated peacefully, she will not have this persona anymore. 
- Main Article: Phone Addict
Students who regularly have their phones out have this persona. If they witness a murder or see a corpse, they will snap a photo and text it to the police, either leading to an instant Game Over if Yandere-chan is actually in the picture or triggering the police timer to start if she is not. Excluding Cowards, students without this persona will behave as though they have this persona if they have their phone out when discovering a corpse or witnessing murder; however, they will take longer to text the police.
- Main Article: Sleuth
This persona has not been implemented yet. Every student in the Photography Club will have this persona. If School Atmosphere is low, they will continuously search for the criminal to snap a picture of them. If they take an incriminating picture of the player, they will send it to the police, and this will result in an instant game over.
- Main Article: Social Butterfly
When witnessing a murder, Social Butterflies will run to the nearest crowd and then call the police. It is harder to murder around students with this persona because of the number of students that gather and can witness Yandere-chan's actions. If a Social Butterfly sees Yandere-chan after witnessing murder, they will scream and attract attention to them, then will crouch on the ground holding their head. They will happily pose if she takes a picture of them.
- Main Article: Spiteful
When witnessing the murder of a student with low reputation or a student who bullies them, Spiteful students will approve of Yandere-chan’s kill and promise not to tell anyone. If they witness the murder or corpse of a regular student, they will run out of the school and call the police. Spiteful students will give Yandere-chan an annoyed look and cover their face if she attempts to take a picture of them.
- Main Article: Strict
Almost all teachers have this persona. Strict NPCs will expel Yandere-chan if she is caught misbehaving. They will be reported of murder by Teacher's Pets. If a teacher sees a corpse, they will call the police and then guard the corpse until the police arrive. Teachers give the player a suspicious look if she tries to take a picture of them. If she murders a student in front of a teacher, they will chase and restrain Yandere-chan.
- Main Article: Teacher's Pet
Teacher's Pets will run to their favorite teacher and tell them about Yandere-chan's kill. Teacher's Pets will give her a suspicious look if she tries to take a picture of them.
- If a student with the Teacher’s Pet persona discovers a corpse or witnesses murder, they will run and tell a teacher.
- If a teacher is informed of a murder, they will run to the scene of the crime and investigate it.
- If a Teacher’s Pet witnesses a murder/corpse, but someone else is already reporting a murder/corpse, then the student will run and hide in a classroom instead of informing a teacher.
- If a Teacher’s Pet informs a teacher of a murder/corpse and leads the teacher to the scene of the crime after the player has already cleaned up the evidence, the teacher will conclude that the student was pulling a prank on her, leaving the student mentally scarred.
- If a Teacher's Pet reports a murder and then Yandere-chan moves the body far away from the crime scene, even if no other evidence has been cleaned up, the teacher will conclude that the student was pulling a prank on her and will not call the police. However, the teacher will discover the evidence at the end of the day, as normal.
- Main Article: Violent
All the delinquents have this persona. If they see Yandere-chan carrying a weapon, they will prepare their own weapons in response and taunt her until she either initiates a fight, or they get bored and leave. If Yandere-chan gets too close with her weapon out, a combat mini-game will start.
If they see Yandere-chan kill someone, or carrying a corpse, they will fight her until Yandere-chan gets knocked out, or until Yandere-chan kills them. If they witness the corpse or murder of a bully, they will react like students with the Spiteful persona.
- Hero Complex (Became Heroic)
- Sadistic (Became Evil)
- Social Butterfly (Re-implemented as of February 1st, 2016)
- Tsundere (Became Lovestruck)
- Evil (Became Spiteful) (Can be accessed via JSON)
- YandereDev has considered adding a vigilante/perfect student persona, but has not fully decided yet.
- It is also unknown if this has become the Sleuth persona.
In the future, if students have witnessed homicide or corpses enough, they will become "Broken". If they see any more murderous activity, they will not react to corpses or murder anymore.
Can be seen by unlocking all student information by pressing the S key in the debug menu and checking the second reserved student slot. If given to a student, they will automatically apprehend Yandere-chan, should she try to kill them, and will apprehend her if they witness her commit murder.
In the future, one of the Martial Arts Club students may have the "Shrine Maiden" persona.
Only accessible via JSON, this persona will glitch out the student who is given it. Students with this persona will stalk Yandere-chan and try to catch her in the act of murder.
- It may be possible that if tortured, students' sanity will go down in different amounts depending on their persona. Strength will not be a factor.
- If a student witnesses murder, they will hide their face when Yandere-chan aims a camera at them, regardless of their persona.
- Students will act on their persona if they discover their crush's corpse. If they have an interaction event with their crush, but their crush is dead, then they will go to the event spot and mourn. Some emotional NPCs might weep.
- YandereDev planned to include about five personas in the final game. Now the expected number of personas has been exceeded.
- YandereDev would like all personas to have different idle animations when paranoid.
- YandereDev doesn't think that gender-specific personas are a good idea.