Serge Flora, Crown Prince of the Flower Star, initially appears as a mysterious human photographer traveling Europe. His mission tracks the search for the legendary Flower of Seven Colors while documenting human experiences with nature. He frequently encounters Lunlun during her journey, offering subtle guidance and support without immediately revealing his royal status or connection to her quest.

As a photographer, he observes and intervenes indirectly by providing people Lunlun helps with packets of flower seeds. These seeds symbolize specific life lessons through the "language of flowers," such as giving thistles to represent independence after someone resolves to follow their own path, reinforcing the thematic connection between floral symbolism and human emotions.

He develops genuine affection for Lunlun, reciprocating her feelings while concealing his true identity as the Flower Star prince. When the magical flower is discovered, he reveals his heritage and proposes marriage, offering Lunlun the position of queen. Faced with her refusal to leave Earth and her grandparents, he chooses to abdicate his throne, transferring rulership to his younger brother to remain on Earth and build a life with Lunlun.

In the movie *Hana no Ko Lunlun: Konnichiwa Sakura no Sono*, he travels to Japan during cherry blossom season. There, he aids Lunlun in confronting Togenishia and Yabouki's attempts to destroy the blossoms using pollution-based magic. He contributes technology designed to counteract pollen-based attacks and pollution effects, assisting in preserving the cherry trees, aligning with his established character of providing support during environmental challenges.

Visually, he is consistently depicted wearing a distinctive feather hat. He functions as a protective figure and emotional anchor for Lunlun throughout her adventures, ultimately prioritizing their life together on Earth over his responsibilities to the Flower Star.