Yandere-chan
Ayano Aishi is the protagonist of Yandere Simulator. She is known as "Yandere-chan" to players of the game, and has been given the cute nickname "Yan-chan" by her classmates.
Since early childhood, Ayano has suffered from an inexplicable, incurable condition. In short, this condition leaves her with a perpetual sense of being empty, hollow, and incomplete. As a result, she has never been able to experience satisfaction, fulfillment, or happiness, and has not been able to experience emotions in the same capacity as other people. As she grew older, she learned to pretend to be a normal person in order to avoid drawing negative attention from others, but was never able to feel any degree of empathy towards other human beings.
On the first day of her second year of high school, Ayano came into physical contact with "Senpai". In that moment, she gained the ability to experience everything that had been missing from her life; she felt complete, she felt fulfilled, she felt powerful emotions. Meeting Senpai was like seeing color for the first time, hearing music for the first time, and feeling warmth for the first time. In his presence, she felt overwhelmed with euphoria...but as soon as they were apart, the feelings of emptiness returned.
Within a very short span of time, she quickly became absolutely addicted to him, and came to rely on him in order to feel alive. Then, Ayano saw something horrible...something that terrified her and infuriated her at the same time. It was a young woman who clearly had deep feelings for Senpai. If Senpai entered a relationship with this girl, then Ayano might lose him forever...
Without a moment's hesitation, Ayano knew exactly what had to be done. This girl - her rival - had to be eliminated as soon as possible, by any means necessary, no matter what the cost.