|Role|| Main character|
At the moment, Taro Yamada is his placeholder name. Taro Yamada is the Japanese equivalent of "John Doe". John Doe can refer to a hypothetical person whose real identity is unknown. If Senpai is female, her name will be Taeko Yamada.
Senpai's name will never be spoken aloud, but it will appear in the Student Info screen and on in-game social media. The player may be able to pick Senpai's name in a future build. In the official game, the player will be able to choose Senpai's gender. However, Senpai's original gender is male; therefore, the article will refer to him as such.
- Main Article: Intros
In the first intro cutscene, he was first seen in Yandere-chan's dream, where the player can customize him. The next morning, Yandere-chan, who was late to school, bumps into him and immediately becomes obsessed with him. Senpai, however, doesn't know this, and will accept the love confession of any girl who chooses to do so. Right after he meets Yandere-chan, he is scolded by Osana Najimi and they walk the rest of the way to school together, with a lamenting Yandere-chan watching from afar. Info-chan watches the entire scene from behind them.
In the second intro, Senpai is not seen outside of customization. However, Info-chan calls Yandere-chan out on stalking an upperclassman, and tells her that the girl he was with is named Osana Najimi.
Appearance (Default Look)
Senpai, with his default look, has short, messy dark hair, charcoal grey eyes, light skin, and the default male school uniform with gold buttons and black cloth. This is his default look because he is meant to look like a generic male anime protagonist.
Upon starting the game, the player can customize his gender, skin tone, hairstyle, hair color, eye color, eyewear and facial hair, but if no changes are made or the process is skipped, Senpai will appear with his default look. Senpai is the same height as every other male student in the game so that all animations can link up. If possible, YandereDev would want Senpai to be slightly taller. YandereDev might release Senpai's textures and put them in the Streaming Assets folder so that the player can make custom skins for Senpai.
He is the only character highlighted pink in Yandere Vision.
"The Japanese word "senpai" refers to someone who has seniority over someone else. For example, if you are a first-year student, all second-year and third-year students are your "senpai". If you start working at a new job, any co-worker who has been employed at the workplace longer than you is your "senpai".
In Yandere Simulator, the title of "Senpai" is given to the young man (or young woman) that the protagonist is infatuated with. The player is given the option of choosing Senpai's gender at the beginning of the game; they might be "Senpai-kun", or they might be "Senpai-chan". If Senpai is a male, his name is Taro Yamada, and if she is a female, her name is Taeko Yamada.
Over the course of the school year, ten different girls will fall in love with Senpai. There is a myth at school that if a girl confesses her love to a boy under the cherry tree behind the school on a Friday, the two of them will love each other forever. Every girl who falls in love with Senpai plans to confess at 6:00 PM on Friday. For Yandere-chan to prevent the love confession from taking place, she has to eliminate the rival before 6:00 PM on Friday .
The first intro portrays Senpai as kind and considerate. He helps Yandere-chan up after he bumps into her and is seemingly friendly.  He doesn't resent Osana Najimi for her hostility toward him and just follows her orders.
Senpai may also be somewhat of a pushover; he doesn't protest Osana's rude behavior and will accept any confession he receives, which is why Yandere-chan must eliminate her rivals before they confess.
The second intro's Senpai isn't characterized nearly as much as the first. His personality is never mentioned by Yandere-chan or Info-chan. He still accepts the confession of any rival with a good enough reputation, which might imply that he's still rather meek. However, this could be because he's on good terms with all the rivals.
His personality will be shaped and molded by the way that people around him are disappearing.
- If the rivals are paired off with suitors, Senpai will think that he is not as appealing as other boys.
- If rivals mysteriously stop coming to school, then he will assume all girls are delinquents who skip school.
- If rivals show up dead shortly after they talk to him, Senpai will wonder if he is cursed.
- If Senpai has to reject many rivals because he can't get along with any girl he meets, then he will worry that he will never find a partner.
Depending on the Yandere-chan's actions, Senpai might develop PTSD, a personality complex, a nervous disorder, or social anxieties.
He seems oblivious to Kokona's affections, judging by how she laments that he never notices her feelings when talking about him. Senpai never seems to realize why Yandere-chan follows him around and only asks her to leave him alone if she gets too close.
He is a loner who enjoys nature more than the company of people. Though an introvert, he does not seem to be shy. Senpai is not popular in the beginning, although girls will fall in love with him over the course of the game. Some popular people might even notice him. He is normally gentle and prefers solitude, but would feel enraged upon witnessing a masked killer, and unmask them without regard for his own safety.
He is an average male student who gets average grades.
A backstory has never been fully written for Senpai. He is meant to be plain and average.
In the original intro, Osana Najimi was his childhood friend. They have apparently known each other for a decade.
The reason Senpai is so popular is because he sat in the "Main Character Chair". From that moment on, his fate and destiny were set in stone.
Senpai has a younger sister, whose gender will not change if there is a female Senpai. Senpai's parents look very ordinary. His father looks like an older version of him, and his mother looks as plain as he does. If they suspected he was in danger, they would move town for him.
Info-chan cannot dig up any dark secrets about Senpai because he apparently has no dark secrets at all.
At 7:05 AM, Senpai enters the school grounds. He walks to his locker at 7:10 AM and changes from his outdoor shoes to his indoor shoes. At 7:15 AM, he walks to the fountain and sits on its edge, reading a book. He does not socialize with the other students.
At 8:00 AM, Senpai walks into Classroom 3-2 and sits at his desk. He starts his morning classes at 8:30 AM, and leaves to go to the rooftop to eat his bento at 1:00 PM. On Wednesday, Kokona Haruka watches him from behind a tree.
Senpai walks to class again at 1:30 PM and finishes his afternoon classes at 3:30 PM. Afterwards, he will remain reading at the fountain until the school day ends. No matter what time the player chooses to leave school, Yandere-chan always watches him go home until he arrives at his house safely.
Senpai is more similar to a "moving obstacle" rather than a regular interactive student. If a small town is added, it's possible there may be a "date gameplay" mechanic.
Staying near Senpai will cause Yandere-chan's heart to beat loudly and the screen to turn pink. Yandere-chan will drop anything she's currently holding, keeping her hands to her chest. She cannot do anything besides walk slowly when she is near him. Entering this zone will help her recover lost sanity. In the future, Yandere-chan's animations while near Senpai will look much weirder and she will appear to be extremely anxious. If Yandere-chan stands in Senpai's line of sight for too long, he will get slightly freaked out, and slowly lose patience. If this happens five times in one day, he will yell at her to go away, causing Yandere-chan to become heartbroken and trigger an immediate Game Over. If Yandere-chan is in the Occult Club, or plays the "Stealth" game in the computer lab, she can then stay in Senpai's aura for longer without being noticed.
If he sees Yandere-chan performing suspicious actions such as holding a weapon, dragging a corpse, having low sanity, being covered in blood, killing a person or taking a panty shot, it will trigger an immediate Game Over as well.
Since Senpai is a Loner, he will run away when he sees a corpse on school grounds, if Yandere-chan is not there to alert him in some way.
Senpai will have a hidden sanity variable that will influence some of the game's endings and might influence his everyday behavior.
Normally he cannot be killed like a normal student due to his aura. Certain Easter Eggs can still kill him, but he will respawn the next day.
- Main Article: Rivals
In the full game, Senpai will be on good terms with all the rivals, so he won't suspect them of any crimes even if he sees them covered in blood. If there's "evidence" against a rival, however, he will be unable to stop them from getting arrested.
- Main Article: Osana Najimi
YandereDev has not revealed why Senpai chooses to spend time with Osana, despite her treatment of him. After she is eliminated, there may be a cutscene showing how Senpai is handling the situation.
- Main Article: Yandere-chan
Senpai isn't close with Yandere-chan and doesn't know much about her. He usually never notices Yandere-chan, as she is able to follow him home after school, depending on how the day went. However, if she stands near him for too long during the day, then he notices her and is creeped out by her behavior.
- Main Article: Kokona Haruka
Senpai is oblivious to the test rival, Kokona Haruka's feelings. They are in the same class as each other, but she still calls him Senpai.
- Main Article: Hanako Yamada
She and Senpai are brother and sister. If Hanako ever got a boyfriend, Senpai would be sad that he is no longer the center of her world, however, he would be happy that she is finally independent from him in a bittersweet way.
If she is killed, Senpai's sanity variable will greatly decrease.
At the end of Hanako's week, she will force her brother to agree that he'll never get a girlfriend.
- Main Article: Muja Kina
In the final game, Senpai will become sick for the one week that the school nurse isn't present. Instead, he will visit Muja Kina every day. Senpai will become attracted to her, and their relationship may grow.
- Main Article: Uekiya Engeika
If none of the rivals ended up affecting Senpai's love life, he would likely enter a relationship with Uekiya, since the Gardening Club is the one club that he actually ever seriously considered joining.
- Senpai's favorite food is still undecided.
- Senpai wrote a book, How to Hentai without Hentaing, seen in the May 7th, 2015 Build. This object was later removed; YandereDev has since declared it non-canon.
- The book was reintroduced with a different cover in the December 16th, 2016 Build. It can be found inside the safe, which can be opened with a key during Mission Mode.
- In old builds, Senpai was usually the first to naturally witness Kokona Haruka's corpse if Yandere-chan poisoned her at lunchtime, as he stood closest to where her corpse would be and would spot it as he headed back to class at the end of his lunch break. However, as of the November 15th, 2015 Build, Kokona's corpse is no longer in Senpai's path as he returns to class, and he will not discover it.
- Senpai's voice lines for the poisoning event, as shown in "How to poison a girl in Yandere Simulator", were not in the actual game.
- The character model that was used to make Senpai is available in the Unity Assets store under the name Taichi Hayami.
- In the future, it will be possible to steal Senpai's clothes and shoes from the gym. YandereDev has said that the game mechanic of stealing items from Senpai for the Senpai Shrine has been planned since its implementation.
- In Japanese, senpai (先輩) means upperclassman.
- The only way to kill Senpai is to use unconventional methods, such as Easter Egg modes. However, it will have no effect on the end of the day, and the ending words still say that Yandere-chan sees Senpai walk back home (unharmed). Senpai will respawn the next day.
- If Senpai was in a Hogwarts house, he would be a Hufflepuff.
- There are 25,000 different combinations of customization options for Senpai - 150,000 different combinations if Senpai is in a customized uniform.
- Senpai has never bought a panty shot from Info-chan.
- Senpai has an unnamed career path that has not been revealed yet.
- Senpai can probably cook a few simple meals.
- On Akademi High School's Facebook page, there is a post made by Senpai asking how old the sakura trees are.
- Senpai's birthday might be the same as Yandere-chan's birthday, April 1st.
- On December 23rd, 2015, YandereDev posted a comic created by Achromatic, which joked about what would happen if Senpai was allergic to cats. If Senpai was ever allergic to cats, Yandere-chan would kill her own beloved cat for him. However, Senpai being allergic to cats is not necessarily canon yet. The comic can be viewed on YandereDev's website
- There was an old idea of breaking into Senpai's house, but it depends on whether or not there will be a small town in the game.
- YandereDev states that Yandere-chan could possibly go on a date with Senpai, if a small town was added.
- In the February 17th, 2016 Build, Senpai was shown in his student profile as darker skinned, blond with spiky hair, and wearing shades. He was made to look that way because YandereDev was testing out new customization features and forgot to reset him.
- Senpai did not have a voiced line for reacting to Yandere-chan taking panty shots until the March 31st, 2016 Build.
- Senpai doesn't appear in Mission Mode.
- If too many girls die or go missing immediately after meeting Senpai, rumors may spread that he is a serial killer. 
|“||Are you...okay?/Can I...help you?/Is something...wrong?/I'm...a little concerned...||”|
— Senpai after he spots Yandere-chan harassing him.
|“||Hey, cut it out! That's really creepy! Leave me alone!/Um, excuse me! Would you please stop doing that? You're scaring me!||”|
— Senpai after being harassed too long.
|“||What the hell is wrong with you?! Get away from me!||”|
— Senpai after seeing Yandere-chan visibly insane/laughing maniacally/possessed by the Pain Demon.
|“||Why do you have a weapon? What are you going to do with that thing?! Stay back!||”|
— Senpai after seeing Yandere-chan visibly armed.
|“||Why do you have so much blood on you? Did you hurt somebody?||”|
— Senpai after seeing Yandere-chan covered in blood.
|“||You killed them! Stay back! Get away from me!/What have you DONE?! You MONSTER!/Oh my god! You just MURDERED someone!/How could you do that?! Do you realize what you've just done?!/This can't be happening! Somebody, help! HELP!||”|
— Senpai after seeing Yandere-chan murder someone or near a dead body.
|“||What the hell are you doing? That's horrible! Stop it, you creep!||”|
— Senpai after seeing Yandere-chan taking panty shots.
|“||Does anyone know how old the school's sakura trees are?||”|
— Senpai on the internet.
|“|| Wow! This is delicious!|
Yeah! It's great!
Hmm? What was that?
— Senpai in "January Osana Progress Report - Part 1".
|“|| Ugh... what did you put in this?!|
My stomach... really hurts all of a sudden!
I'm sorry... I can't finish it! I have to go!
— Senpai in "January Osana Progress Report - Part 1".
|“|| What's this?|
You made me lunch?
Oh...cool! Thanks a lot!
— Senpai in "January Osana Progress Report - Part 2".
|“||Osana? Are you okay? What's wrong hey?! Do you need any help? Osana! Oh my god! Osana, answer me! Wake up, please wake up! Don't do this! Oh god, this can't be happening! No!||”|
— Senpai in "January Osana Progress Report - Part 2".