Rivals are the main antagonists of Yandere Simulator. In the future, there will be ten rivals for the ten weeks of Story Mode, with one rival appearing each week. They have not been fully implemented yet.
They are the most important people to eliminate, as they all have a crush on Senpai. If the rival is not eliminated by the end of the week, they will confess their love to Senpai under the Sakura Tree behind the school on Friday and Yandere-chan will be left heartbroken. The only exception to this is Senpai's sister, Hanako. A girl confessing to a boy underneath a cherry tree is a cliché in anime that will be drawn upon in the game. Each rival in the game is an anime archetype, inspired by popular concepts and stereotypes. However, not every one of them is based on a "dere" archetype.
In the current debug build, there are no actual NPCs who function like proper rivals, so there is no way to win the game yet. In the full game, they will not be in the school until their week comes. Each rival will be introduced via a cut-scene conversation with Info-chan. The rivals for weeks two to ten will each have areason for not coming to the school for the previous weeks of the game. They will also have a short cut-scene that shows how they met Senpai and why they are attracted to him. Some of the cut-scenes will be humorous to balance out the other dark elements of the game.
Senpai will not fall in love with girls of his own accord. He will start to develop a crush on a rival if she has five interaction events with him. There will be one "event" with Senpai each day, with the final event being a love confession. It is possible for Yandere-chan to sabotage each event.
Even though the main object of their desire is Senpai, all rivals will have a secondary crush on a male student. This allows the main character to matchmake every rival with their suitor as a way of eliminating them. If the player chooses to make Senpai female, then Yandere-chan and Senpai will be lesbian and all of the rivals will be bisexual.
Every rival will wear special stockings to make themselves stand out and will have unique panties that suit their personality. In the future, rival hairstyles and accessories might be unlocked after beating the game once. YandereDev has considered the idea of allowing the player to dress up as any of the rivals after eliminating them.
As the game progresses, each rival is more difficult to defeat than the previous one, sometimes because of popularity.
Rivals are seen outlined in red in Yandere Vision, although this outline might have other identifications as traumatized students also have a red aura.
The rivals will never know the player exists or that they have competition for Senpai.
All rivals have been planned out. They have had official rival designs since October 2015. As of late November 2015, an artist has created full-body illustrations for every rival character. YandereDev has officially revealed all of the rivals in the Rival Introduction Video and on the Characters Page. Only Oka Ruto and Muja Kina currently exist in the game.
Osana Najimi will be the first rival in the full game. NOTE: The character who stands under the cherry tree is "Rival-chan". Osana will be a completely different character.
Her AI is currently incomplete, so she cannot be interacted with. Furthermore, YandereDev needs dozen of male and female animations before he can add in Osana. Because of this, the player cannot beat the game, and you will always lose on Friday at 6:00 PM due to Osana confessing her love to Senpai. She was originally shown in the first intro to be Senpai's childhood friend and a tsundere.
In the second intro, her tsundere tendencies and her background as Senpai's childhood best friend are not mentioned in the slightest. However, YandereDev says that her character concept has not changed.
Oka Ruto will be a rival in the full game, although she does not currently function as one. She is the founder and president of the Occult Club. She is also a cross between the Hex Maniac from Pokemon: X and Y, Tharja from Fire Emblem: Awakening, and Tomoko from WataMote.
Muja Kina, who is a substitute nurse, is a planned rival. Her character trait is unintentional sexual innuendos. She is pure and innocent. The official nurse will be on vacation during her week as a rival. She will disappear from the school after her week is over, even if she is eliminated peacefully.
Mida Rana, who is a substitute teacher, is also a planned rival. The teacher's trait is intentional sexual innuendos, and she will be sultry and seductive. She can be called upon by a Teacher's Pet if they discover a corpse or witness a murder. Yandere-chan will be able to matchmake her with a student. She will disappear from the school after her week is over, even if she is eliminated peacefully.
Hanako Yamada, who is senpai's little sister, will be the eighth or ninth rival in the full game. Her appearance has been updated as of November 28th, 2015. She does not lust after her brother, but loves him so much that she does not want him to get a girlfriend. She wants to have all of his attention. She is said to be one year younger than Senpai and two school years behind him.