"RahXephon" is a 26-episode anime series that blends mecha action, psychological drama, and metaphysical themes. The story is set in a world where Tokyo has been isolated from the rest of the planet by a mysterious barrier known as Tokyo Jupiter. Within this enclosed city, time flows differently, and its inhabitants live unaware of the outside world. Ayato Kamina, a high school student, discovers that his reality is not what it seems when he encounters Haruka Shitow, a woman from the outside world who reveals that Tokyo has been under the control of an alien race called the Mu. Ayato is drawn into a conflict between humanity and the Mu when he becomes the pilot of RahXephon, a giant biomechanical entity with immense power.

As Ayato pilots RahXephon to defend against the Mu's attacks, he begins to uncover the truth about his identity and the world around him. He learns that the Mu are not entirely alien but share a deep connection with humanity. The series explores themes of identity, memory, and the nature of reality, as Ayato grapples with his past and his role in the unfolding conflict. Key characters include Reika Mishima, a mysterious girl with ties to Ayato's childhood; Quon Kisaragi, a quiet and enigmatic figure who also has a connection to RahXephon; and Makoto Isshiki, a scientist working with the TERRA organization, which opposes the Mu.

The narrative is layered with complex relationships and emotional conflicts, particularly between Ayato and Haruka, whose pasts are intertwined in ways that are gradually revealed. The series builds toward a climactic resolution where Ayato must confront the true purpose of RahXephon and its role in reshaping the world. The story concludes with a focus on the power of music and harmony, as RahXephon is revealed to be an instrument capable of tuning the world to a new reality. The series balances its philosophical undertones with intense mecha battles and character-driven drama, creating a multifaceted narrative that explores the intersection of personal and universal truths.