Rei Ayanami is the First Children and exclusive Pilot of Eva-00. Officially, Rei Ayanami is fourteen years old, but it is stated that all records of her background have been erased. Unusually for a child her age, Rei lives alone in an decrepit apartment. Rei attends Tokyo-3 Junior high school and is a member of Class 2-A.

Rei Ayanami is most famous for her distinctive appearance. She has blue hair, pale skin, and red eyes. It has been stated that Rei's unusual appearance was intended by the creators of the series to make her stand out. Strangely, Rei's unusual appearance is never commented upon throughout the series, even by Asuka.
 
Rei is a vegetarian. This is seen in Episode 12.It is not clear whether this is by choice, or through quirk of her physiology. It should be noted that series creator Hideaki Anno is also a vegetarian, as was Nadia Ra Alwar of Nadia: Secret of the Blue water


Outwardly, Rei can seem somewhat cool and aloof, often spending time on her own reading books. Yet, she can easily be confused by emotions, and is somewhat detached from her own. This is most obvious in Episode 6, when Rei finds her self unsure how she is supposed to feel after being rescued by Shinji Ikari. In Episode 12 Rei did not come to Misato's party, even though she was specifically invited by Asuka. Rei was specifically brought to the synch-training party at Misato's apartment in Episode 09, but that seems to be because Misato actually brought her. Rei isn't simply mysterious to people she doesn't know at first (i.e. during the introductory episodes): Rei is disconnected socially even from the other Eva pilots. When Rei is invaded by Armisael in Episode 23, the Angel forces her to feel her own true loneliness and pain. In the next scene, Rei is shown crying and not even understanding why she is crying. Episode 25 further shows that Rei has a deep despair and a wish to return to nothingness.
 
Rei has been shown to place no value on her own existence. In Episode 19 she states that If she dies, she can be replaced, but it is not unitl Episode 23 that finally the audience understands what she means by this. This is further shown by her indifference towards her own comfort or personal space. In Episode 5, she shows nothing but indifference to Shinji when he accidentally falls on top of her, in what would be seen as a compromising position. Yet, she is also aggravated enough when he makes disparaging remarks about Gendo Ikari to slap Shinji in the face for it.
 
Yet she is also capable of placing value in investing herself in people. She has a strong connection with Gendo Ikari throughout the series. Rei keeps a broken pair of Commander Ikari's glasses as an memento of his rescuing her after EVA-00's failed activation test shown Episode 4. It can be suggested that Rei is seeking to stave off her own despair, by investing herself fully towards the needs of one single person, in order for her to be recognized as a person.
 
As the series progresses, Rei began to distance herself more from the Commander. Meanwhile a bond began to develop between herself and Shinji Ikari; beginning shortly after the attack of the Sixth Angel, Rei was shown talking with Shinji on several occasions, something stated within the series that she almost never does to anyone else. As the series finale approached, Rei eventually chooses Shinji over Commander Ikari and allows Shinji to control Third Impact through her. She also destroys Commander Ikari's glasses, the symbol of her bond with him.