Japanese seiyū: Maaya Sakamoto
English voice actor: Mandy Clark
First appearance: Episode 1
Reika Mishima first appears in the series as the subject of one of Ayato's paintings. She then appears, in person, during the attack on Tokyo in episode 1. She leads Ayato to the RahXephon, and is shown to have some sort of connection to it via her singing.
In episodes #1, 2, and 20, it is hinted that Reika is not a normal human being. She does not have a reflection unless she needs to, she calls Ayato from an unassigned phone number, and she appears to alter Ayato's classmates' memories to make them remember her. She later appears as an aide to Makoto Isshiki, apparently altering TERRA personnels' memories in the same fashion. It is revealed that Reika is actually Ixtli, the soul of the RahXephon, and that her appearance is a manifestation of Ayato's desires. This enables him to connect with and fully use the RahXephon; in artistic terms, she is his muse. Her form is chosen to closely mimic that of a young Haruka Mishima (later Shitow) with whom Ayato had fallen in love. The black RahXephon's Ixtli appears to Quon in the shape of Ayato.
Although Ayato rejects Reika after he learns the truth about her and what she is, he later chooses to accept her and become one with the RahXephon, thus enabling him to re-tune the world.