Lala's gift for Rito's 16th birthday, Celine is a multi-story, carnivorous, sentient sunflower kept in the Yuuki's residence backyard. Although seemingly monstrous, Rito cares for Celine deeply, referring to her as his family. The plant behaves akin to a human: perspiring when the climate is humid, wearing an oversized scarf during a chilly day and eating a bowl of ramen when hungry (though Celine still needs the basic nutrients of water and sunlight). When Celine contracts a deadly disease, Rito is fully dedicated to saving her from Kare Kare and finding the luckyberry. With his friends they journey to an S-level-danger class planet of Misletoe to retrieve an antidote, only to return and find the plant all dried up. In reality, it was germinating and from its single seed burst out Celine, taking the appearance of an infant girl, with a flower on her head. This event even shocks Momo, who is very knowledgeable with the galaxy's flora, stating Celine's biological makeup is still a complete mystery to her.

Referring to Rito as her "mama", the infant Celine develops a low tolerance for cola and can spray a pollen from the flower on her head that temporarily causes anyone who inhales it to fall in love with Rito - a side-effect that originates from Celine's own affection for him from taking care of her everyday. A running gag as a child is Celine will playfully tackle any girl and attempt to breast feed on them. Comically mistaken for being Rito's daughter, Celine as a plant and infant does make an appearance in the animated adaptation.