As of the March 6th, 2018 Build, there are currently fifteen personas that are implemented in Yandere Simulator: Loner, Heroic, Teacher's Pet, Spiteful, Coward, Social Butterfly, Violent, Strict, Friendly but Strict, Lovestruck, Dangerous, Phone Addict, Fragile, Stalker, and Sleuth. YandereDev has confirmed that there will be more personalities. However, more personas would require more animations and having a larger number of students.
Loners, Teacher's Pets, Social Butterflies, and Heroes will act hostile towards Ayano Aishi 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 Ayano'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 Ayano'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 Ayano 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 Ayano and will start begging her to spare their life in exchange for their silence. Cowards will cover their face if Ayano attempts to take a picture of them.
- Main Article: Dangerous
All members of the Student Council have this persona. They will push Ayano away if she gets too close. If she approaches a Student Council member and attempts to attack them or gets shoved by one of them five times, they will spray her with pepper spray. If they see Ayano 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. If they catch Ayano fighting with any of the Delinquents they will run up to them and break up the fight. Dangerous students will not react to having their picture taken.
- Main Article: Devoted
All members of the Aishi family, excluding husbands, have this persona. A Devoted student will perform whatever it takes to achieve someone's love. Specifically, killing their enemies and rivals to achieve this target. Currently, it is the only confirmed persona to not be in the game. The Devoted persona is code for 'Yandere'.  
- Main Article: Fragile
Fragile students will become terrified of Ayano and will start begging her to spare their lives in exchange for their silence. Fragile students will cover their face if Ayano attempts to take a picture of them. Fragile students can be used to eliminate a student if Ayano frames the latter for spreading gossip of the victim. So far, Horuda Puresu is the only student in the game to have the Fragile persona.
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 Ayano. 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 Ayano tries to take a picture of them.
- Main Article: Heroic
If a Heroic character spots Ayano 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 Ayano 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 a murder. They will set apart from other students, making it easier to kill them. Some Loners will cover their face if Ayano attempts to take a picture of them, while others may give her a suspicious look.
- 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 Ayano commit murder, they will run to Senpai and tell him Ayano was responsible, which will cause an instant Game Over.
If a rival is eliminated peacefully, they 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 Ayano 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. Every student of the Gaming Club, excluding Gema Taku, along with the Bullies have this persona. Additionally, all members of the Photography Club will also use the Phone Addict persona if school atmosphere is below 80%.
Can be seen by unlocking all student information by pressing the S key in the debug menu and checking the first reserved student slot. If given to a student, they will automatically apprehend Ayano, should she try to kill them, and if they witness her commit murder. It was first seen as "Protective" earlier in the video "The Photography Club and Sleuths in Yandere Simulator". Raibaru Fumetsu is the only student who has been shown to have this persona. It was previously named "Indestructible".
- Main Article: Sleuth
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. If School Atmosphere is high and they witness Ayano murder somebody, most will react with the Social Butterfly persona. Fureddo Jonzu will react with the Heroic persona instead and will attempt to apprehend her.
- 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 Ayano's actions. If a Social Butterfly sees Ayano 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 Ayano’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 Ayano an annoyed look and cover their face if she attempts to take a picture of them. So far, only Borupen Saishiki has this persona.
- Main Article: Strict
Almost all teachers have this persona. Strict NPCs will send Ayano to the guidance counselor 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 Ayano.
- Main Article: Teacher's Pet
After witnessing the murder of a student, Teacher's Pets will run to their favorite teacher and tell them about what happened. 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 Ayano 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 Ayano gets too close to them they will push them away. If done five times the combat mini-game will start, and the player will have to press the buttons shown on the screen as quickly as possible. They will not push Ayano away if she has completed a task. If they see Ayano 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 Ayano gets too close with her weapon out, a combat mini-game will start.
If they see Ayano kill someone, or carrying a corpse, they will fight her until Ayano gets knocked out, or until Ayano kills them. If they witness the corpse or murder of a bully, they will react like students with the Spiteful persona.
Only accessible via JSON, the students in the Photography Club will take on this persona if they catch Ayano committing murder, and she gets away with it. Students with this persona will stalk Ayano and try to catch her in the act of murder.
- Hero Complex (Became Heroic)
- Sadistic (Became Evil)
- Tsundere (Became Clingy/Damsel)
- Clingy/Damsel (Became Lovestruck)
- Evil (Became Spiteful) (Can be accessed via JSON)
- Vengeful (Became Stalker) (Can be accessed via JSON)
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.
In the future, Mina Rai 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 Ayano 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 Ayano 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.
- As of the March 6th, 2018 build, it is now possible to alter Ayano's persona at any mirror. This grants her benefits with certain groups of students.
- 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.
- The Social Butterfly person was re-implemented as of the February 1st, 2016 Build.