The Mew Mews are young girls who have been injected with the genes of endangered species, giving them the ability to transform into Mew Mews. The project chose endangered species because they felt that these species would have the strongest desire to preserve their kind. These superheroes are biological weapons tasked with fighting the chimera anima, the monsters created when alien parasites infect a living host. They are later called on to fight the aliens that were the source of the Chimera Anima invasion. The creation of the first five Mew Mews occurred accidentally. The head of the project, Ryô Shirogane, originally intended to inject a Chimera Anima with the endangered animal genes directly to see if that would reverse the effects of the infection. Instead, it was accidentally injected into five different girls when the earthquake happened.