An observant and intelligent Liberator who becomes Mamori's partner after arriving on the island with her. She doesn't speak much but is very protective of Mamori and is shown to be very powerful. Despite having a mature appearance, she is actually a year younger than Mamori. She is a former Soldier (code name C7), a member of an experimental military unit which tested Mirei and her partner's A Virus powers for warfare applications. As a result, Mirei's body contains a special ability known as Enhance, implanted nano-cybernetics which grant her enhanced strength but causes a great deal of stress on her body. Because of her unwillingness to kill a defenseless enemy, Mirei was set to be terminated, but was saved by one of the scientists who gave her her enhancement. Driven into isolation, Mirei found in Mamori a new reason to live.