The life of ordinary high school student Kaji Rikuo is abruptly disrupted by the arrival of Vanilla, an adorable girl with cat ears. Vanilla explains that she was engineered by her master, Ibu Kiriko, using a combination of various animal traits, making her something akin to a chimera. Kiriko apparently harbors a grudge against Rikuo. Puzzled by the reason for this supposed vendetta, Rikuo befriends the innocent and charming Vanilla. Nevertheless, Vanilla possesses the ability to transform into a ferocious beast capable of harming Rikuo, triggered by a mere command from Kiriko...