Neiro is one of the main characters from the anime Kaiba.
Neiro is a member of the Issoudan group. In the episode chronology, she is a bitter enemy of Warp and believes that he has killed many of her friends and family. In early episodes there are news reports of her committing terrorist acts on various government facilities.
As the series progresses, she and Popo eventually tracks down Warp and corner him. Popo encourages her to kill Warp but she is hesitant for unknown reasons. Eventually she pulls the trigger on Warp and immediately breaks into tears and it is later revealed that her memory had been damaged and that she had actually had a romantic relationship with Warp (episode 9).
Later in the series it is revealed via flashbacks that, prior to the first episode, Neiro had been a far less enthusiastic member of Issoudan than what we initially saw in the early episodes. Popo sent her to infiltrate Dictator Warp's palace and kill him and Neiro proceeded with the plan but her presence had a profound impact on Dictator Warp, causing him to renounce his ways. The two fell in love but during an attack on Warp's palace both sustained serious injuries. The result was Warp losing his memories and ending up where he was in Episode 1 and Neiro having her memories damaged.
Popo discovers both bodies and, being aware and jealous of her love for Warp and desiring to usurp Warp's throne, alters her memories so that she associates Warp with everything negative in her life and himself with everything positive in her life. Neiro becomes aware of this after shooting Warp and breaking into tears in Episode 9.
During the final episodes, Neiro sneaks into Warp's old palace and confronts Warp, who has gone there to put an end to the damage that he started long ago. Disillusioned from a battle that takes place while doing this, Warp begins to implement a plan to merge everyone's memories so that happiness can be shared amongst everyone (similar to the ideal outcome of the Human Instrumentality Project from Evangelion). Neiro is able to talk him out this and the series ends immediately after.