Misa Amane is a yandere to Light, Keiichi and Raisa in Death Note.
When she was a teenager, she was supposed to die at the hands of a crazy stalker who claimed to be in love with her. Since a Shinigami named Gelus was watching over her, he was able to avert her death by having her stalker die in a different way, which cost him his life since he saved her. Ever since Light killed the man who murdered her family, she had been an adamant Kira supporter. Once she gained her own Death Note and made the Eye Deal, she tried showing her support and newfound abilities in order to make contact with him.
Personality and Yandere Traits
Despite being a grown-up woman, she acts very childishly and naive. She believes that she Kira/Light is her savior because he killed the man who murdered her family. When she finds out that he's Kira, she starts doing research on him and becomes infatuated with him. She swears to be eternally devoted to him and is willing to give up her life if it means helping him in some way. However, when he tells her that they can't be seen together and that he has to be seen with other girls, she threatens to kill them because she wouldn't allow that to happen. During the Mello/Near arc, she expresses jealousy towards Takada for spending time with Light and tells her that she will be executed after Light captures Kira.