Eve is a young girl, who is a genetically engineered bio-weapon. She is able to use nanotechnology to transform her body into various offensive and defensive weapons. Initially only able to alter limited parts of her body, she is later able to transform her entire body at will, though it causes much strain on her body. She generally turns her arms into blades, hammers and shields, turns her hair into fists and microblades able to cut through steel, turns her own skin into steel, sprouts wings from her back to fly and fires the feathers, and transforms into a mermaid in order to swim more efficiently. She is voiced by Misato Fukuen in the Japanese anime and Brina Palencia in the English dub. Fukuen also later voiced Golden Darkness, an assassin based upon Eve in To Love-Ru.

She is designed to be the ultimate soldier, and she is raised to be an emotionless killing machine. However she instead of becoming emotionless she hated killing and simply didn't understand the concept of free choice. She is saved by Sven from the weapon dealer, Torneo Rudman, and he treats her like a human for the first time in her life. She seems to perceive Train as a rival, wanting to replace him as Sven's partner, but this is done for Sven's attention. Additionally, she loves reading, and can remember everything in a book after reading it once. Sven initially tries to keep her away from the Sweeper life for her own safety, though she proves that she can fight as well. Eve has some problems with controlling her fear. Due to her upbringing as a weapon, she never learned how to handle the emotion and that becomes a point on which she is determined to improve upon so she can be of use to Sven. She disliked being treated as a child. Towards the end of the series she had gotten over her fear. She also has a deep sense of compassion and will absolutely not kill no matter what (this stems from guilt she feels for the murders she committed before Sven found her). In the anime, she actually seems to concentrate a little on her feelings for Sven after Layla asks her why she had become a sweeper and she says, "Because someone cherishes me," to which Layla asks, "Oh is he your boyfriend?" Eve doesn't reply but later, when she gets back with Sven, she blushes. However, it seems that her feelings are not very significant for nothing else appears in the anime that shows she still has feelings for him. The reason might be because Sven asks her to join a boarding school, oblivious to the fact that she wants to stay with him forever. In the last episode of the anime, she is seen with short hair and a school uniform. This might indicate that she has decided to go to a boarding school. In the manga she seems to view Sven as a father figure rather than a romantic interest.

She is usually called "princess", or "Hime-chan", by Train.