Misaki Nakahara is a central figure in Welcome to the NHK, a mysterious high school girl who lives with her aunt and uncle in a mansion that overlooks the apartment of Tatsuhiro Satou. Her background is marked by severe trauma: her father died when she was very young, her mother remarried an abusive stepfather, and after enduring long-term domestic violence, her mother died by falling from a cliff—a death Misaki witnessed. She was then raised by the abusive stepfather until she moved to Tokyo to live with relatives. She has dropped out of school, and carries a deep conviction that she is the source of misfortune for those around her.

Personality-wise, Misaki is eccentric, intelligent, and perceptive, often reading beginner psychology books to try to understand others. She presents herself as cheerful, demure, and helpful, but this facade masks profound insecurity and a low opinion of herself. She is deeply codependent and needs to be needed; she seeks someone she can define as being worse off than herself in order to feel superior and necessary. This leads her to approach Satou and propose a "big project" to cure his hikikomori lifestyle, which she frames as a contractual arrangement. Her motivations are driven not by pure altruism but by a desperate need for validation and love—she wants to be loved but does not know how to love herself, so she tries to engineer a relationship in which Satou becomes dependent on her.

In the story, Misaki serves as the primary agent of change. While Satou is passive, she drives nearly every major plot development: she initiates their counseling sessions, pushes him to socialize, saves his life when he attempts suicide, and later her own suicide attempt forces a critical turning point. She is the one who proposes a "love contract" and later a final contract in which they dedicate their lives to each other. Her role is that of a self-appointed savior who ultimately reveals her own brokenness.

Her key relationship is with Tatsuhiro Satou. She observes him from her window, selects him as her project, and gradually develops genuine emotional investment, though their bond remains codependent and fraught with manipulation. She also has a strained relationship with her aunt and uncle, who involve her in religious recruitment, and she appears to have no friends outside of Satou.

Misaki undergoes significant development. She begins as a cynical manipulator, acknowledging that she picked Satou because she thought she had finally found someone worse than her. Over time, however, her carefully maintained mentor persona cracks as she becomes genuinely attached. When Satou rejects her love contract, she feels completely unneeded and attempts suicide. After being hospitalized, she leaves a note and tries again, but Satou's intervention and a shared delusion about a conspiracy lead to a new understanding. In the end, she offers a revised contract stating that they will dedicate their lives to each other and die together, leaving their future ambiguous but hinting at a fragile, mutual hope.

Notable abilities include her use of basic psychological strategies, her persistence in maintaining the contract, and her ability to read people's behavior despite her own inexperience. She has no physical powers; her impact is entirely emotional and psychological. Her small stature and fragile appearance contrast with her determined, sometimes manipulative actions.