Chimera (キメラ) is a water flea-like chimera that is with the 2nd year students, Mana and Meisa. It's also a Coppelion because it was genetically engineered to have radiation antibodies. It has a very fast recovery rate ability, it was able to restore its severed arms after a few minutes.
This creature has brain functions at the same level as a human. Furthermore, it appears to be very intelligent as seen reading the Coppélia book and during the Roppongi Hills infiltration it was reading a book about Einstein's Theory of Relativity.
The Chimera was created and first sent into Tokyo by the Three Professors as a "prototype" for testing on the Coppelion's radiation antibody whether or not it works.
The Chimera has feelings and emotions as seen with how it interacts with both Mana and Meisa. Ibara states that the Chimera and the second years have a strong connection towards each other - they were both abandoned by the scientists and the government as failed test subjects.