Cateau serves as one of two primary animal companions aiding Lunlun Flower on her quest. This feline originates from the Flower Star, dispatched to Earth alongside canine partner Nouveau. Their mission is to find a human descendant capable of locating the magical seven-colored flower, essential for the Flower Star's royal succession.

Cateau and Nouveau encounter Lunlun in France on her fifteenth birthday, recognizing her lineage through her mother as a Flower Star descendant. They recruit her for the quest, accompanying her as guides and supporters during travels across Europe and Northern Africa. Cateau actively helps individuals the group meets, aligning assistance with their mission's benevolent goals.

The character demonstrates consistent loyalty and teamwork with Nouveau, jointly confronting recurring antagonists Togenishia and Yabouki. These confrontations involve thwarting schemes aimed at derailing Lunlun's quest or stealing the magical flower. Cateau maintains this supportive role throughout all fifty original series episodes and appears in the theatrical short *Hello Cherry Country*, where the group visits Japan to protect cherry blossoms from pollution and villains.

Cateau's true nature extends beyond ordinary feline traits, being fundamentally an inhabitant of the Flower Star assuming animal form. This origin explains the character's capacity for human-level intelligence, speech, and comprehension.

The upcoming Chinese-produced sequel *Hua Xianzi: Zhi Mofa Xiang Duilun* features a different magical girl protagonist and black cat companion.