At the start of the series,a young girl named Ichigo Momomiya attends an endangered species exhibit with her crush and future boyfriend,Masaya Aayama. After an earthquake,Ichigo and four other girls are bathed in a light. A cat appears before Ichigo,then merges with her. The next day she begins acting like a cat and,after meeting Ryo Shirogane and Keiichiro Akasaka,learns she was infused with the DNA of the iriomote cat. Ryo and Keiichiro explain that this allows her to transform into Mew Ichigo,a powerful heroic cat girl. She is odered to defeat chimera animals-alien parasites-which infect animals and turned them into monsters. Ryo and Keiichiro instruct Ichigo to find the four 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 Lorekeet,Lettuce Midorikawa,a meek but smart girl who endures constant bullying and absorbs the gene of 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 Gray Wolf.

The five mew mews battle the kirema animals 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 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 was in danger of losing when the mysterious Blue Knight appears and rescues her. He returns periodecally 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 the humanity. After explaining to Ichigo that Masaya was a false form for tempory use,Deep Blue attack the mew mews. Masaya's personality briefly reappears and he uses a nearbymew 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. Ryo 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.