The inspiration for this story comes from the American cartoon "The Powerpuff Girls." Professor Utonium and his son, Ken, are analyzing a bizarre substance known as Chemical X. However, when a mochi cake accidentally falls into the mixture, it transmutes into a new compound named Chemical Z. Ken shoots a beam of Chemical Z at an iceberg in Tokyo Bay, which creates peculiar black and white rays that scatter across the city. The black beams mutate some individuals into monsters, including a zoo monkey that becomes the infamous Mojo Jojo. On the other hand, the white beams grant three average girls, Momoko, Miyako, and Kaoru, the ability to transform into superheroes, known as the Powerpuff Girls Z!