Yumi (Sayaka in Japan and Europe) is one of the main characters and the second main female in Ape Escape 3. She is the first and only playable heroine in the main series, and is one of the two characters you can pick to play as, the other being her twin brother Kei. Like Ape Escape 2's main star, Jimmy, Yumi has not made another playable appearance since. But unlike Jimmy, both she and Kei make cameos since then and she also appears in the anime.
She and Kei save the world from Specter's evil plots, just after they and their aunt fail to be hypnotized by the mind control on television.
He is also Yumi's brother. They are supposedly twins, given that they are both in the fourth grade. Their aunt, Aki, fills a role similar to Natalie in the original Ape Escape, in that she provides the siblings with new Gadgets and Morphs. In Saru Saru Big Mission he appeared as one of the hostages of Yellow Monkey (whom he was trying to avoid "marriage" with Yellow, which was actually a doll) and Pink Monkey that Spike and Natalie have to rescue. He is voiced by Hope Levy in the American version.