At the start of the series, a young girl named Ichigo Momomiya attends an endangered species exhibit with her 'crush' and future boyfriend, Masaya Aoyama. After an earthquake, Ichigo and five other girls are bathed in a strange light. A cat appears before Ichigo, then merges with her. The next day she begins acting like a cat and, after meeting Ryô Shirogane and Keiichirô Akasaka, learns that she was infused with the DNA of the Iriomote Cat. Ryô and Keiichirô explain that this allows her to transform into Mew Ichigo, a powerful heroic cat girl. She is ordered to defeat chimera animals—alien parasites—which infect animals and turn them into monsters. Ryô and Keiichirô instruct Ichigo to find the five other girls from the exhibit—the remaining Mew Mews. They are Mint Aizawa, a spoiled, wealthy girl who is infused with the genes of the Blue Lorikeet; Lettuce Midorikawa, a shy but smart girl who endures constant bullying and absorbs the genes of the Finless Porpoise; young Pudding Fong, who receives the genes of the Golden Lion Tamarin; and Zacro Fujiwara, a professional model infused with the genes of the Gray Wolf.
The five Mew Mews battle the kirema animas and their alien controllers, Kish, Pie and Tart. Kish falls in love with Ichigo; he tries to gain her love despite the fact that he is trying to eliminate the other Mew Mews. Two more aliens, Pie and Tart, later join Kish in trying to destroy the Mew Mews.
As the fighting intensifies, the Mew Mews are tasked with finding "mew aqua," a material created from pure water that contains immense power for combating the alien attacks. During a battle with Kish at an aquarium, Ichigo is in danger of losing when the mysterious Blue Knight appears and rescues her. He returns periodically throughout the series, protecting Ichigo from various dangers; it is later revealed that the Blue Knight is in fact Masaya. Shortly after this discovery, Masaya collapses and transforms again, into Deep Blue—the alien leader who wants to destroy humanity. After explaining to Ichigo that Masaya was a false form for temporary use, Deep Blue attacks the Mew Mews. Masaya's personality briefly reappears and he uses a nearby mew aqua drop to destroy Deep Blue, killing himself in the process. Crying over his body, Ichigo pours her power into Masaya to save his life, losing her own in the process. Masaya kisses her, changing her back to a human, and revives her. Ryô gives Pie the remaining mew aqua to save the aliens' world, after which Kish, Pie and Tart say their goodbyes and return to their own world. (source: Wikipedia)