When ordinary high school student Kaji Rikuo's routine is disrupted by the arrival of a charming girl donning cat ears named Vanilla, everything takes an unexpected turn. Vanilla discloses her unique origins as a chimera-like creation of her master, Ibu Kiriko, who harbors a grudge against Rikuo. Puzzled by this inexplicable vendetta, Rikuo befriends the innocent and adorable Vanilla. Little does he know, Vanilla has a dark side, capable of transforming into a ferocious beast under Kiriko's control, posing a threat to Rikuo.