Nouveau, a talking dog emissary from the plant spirit realm of Flower Star, journeyed to Earth alongside the talking cat Cateau. Their mission: locate a descendant of their people capable of finding the magical seven-colored flower needed to appoint Flower Star's new ruler. In France, on her fifteenth birthday, they identified Lunlun Flower through her mother's lineage and recruited her for the quest.

As Lunlun's loyal companion and protector, Nouveau traveled across Europe and Northern Africa. He actively aided humans they met, frequently confronting interference from antagonists Togenishia and Yabouki. Nouveau provided emotional support to Lunlun and collaborated with Cateau to overcome obstacles. His vulnerability surfaced during the Norway arc when the villains kidnapped and nearly drowned him to manipulate Lunlun.

Nouveau communicated with humans in his dog form, though his true nature was that of a Flower Star humanoid. This identity remained consistent across all media, including the main television series, the theatrical short "Hello Cherry Country" (featuring his trip to Japan with Lunlun), and later adaptations. He stayed a steadfast presence focused solely on the mission.

The quest concluded with Nouveau witnessing the growth of the seven-colored flower in Lunlun's grandparents' garden, achieved from the seeds collected during their travels. This fulfilled his original mandate from Flower Star's king. Following Lunlun's choice to stay on Earth with Serge, the Flower Star prince, Nouveau's subsequent role or return home is not detailed.