Celsia Marie Claire is an elven priestess who becomes an unwilling guide and ally to a group of humans transported from Japan to her magical world. She is initially introduced as a powerful figure within elven society, but her life takes a chaotic turn when she attempts to send the three humans back to their home. During the casting of this return spell, she loses her concentration, causing the enchantment to shatter into fragments that scatter across the land and imprint themselves onto the skin of various elves. This failure serves as the central conflict of the story, binding her fate to that of the humans until the spell can be restored.

Her personality is a study in contrasts. On one hand, she tries to present herself as a level-headed and mature leader, but this facade frequently crumbles, especially in her dealings with the martial artist Junpei. Their relationship is characterized by constant bickering and public conflict, as she is easily provoked by his rude and tactless behavior. Despite this, her actions reveal a deep-seated determination to get the humans home, not only to save her world from the chaos they inevitably cause but also because she harbors secret romantic feelings for Junpei, which she vehemently denies through their combative interactions. Other descriptions characterize her as being a bit psychotic, a trait that emerges from the immense stress and humiliation of her situation.

Celsia's role in the story is that of the magical expert and the primary means of recovering the lost spell fragments. While the human group travels in a tank and uses brute force to locate elves, it is Celsia who possesses the ability to transfer the spell fragments from the skin of other elves onto her own body. This process is not without significant personal cost. Because she personally extracts the fragments, they become cloven or stuck to her. This mechanic leads to her most notable and unfortunate predicaments: becoming trapped in animal forms. After a willing transformation into a dog she names Pochi to help the group, she recovers a fragment while in that state, locking her into the canine shape for a significant period. Later, she suffers a similar fate, becoming stuck in the body of a small panda bear due to a magical curse. Her journey is therefore marked by a constant loss of dignity as she endures these bizarre transformations while trying to maintain her authority.

Her key relationships revolve around the three humans. With the actress Airi and the military enthusiast Ritsuko, she maintains a functional, if often exasperated, alliance. However, her connection with Junpei is the emotional core of her character development, moving from pure animosity to a grudging, unspoken affection. Her standing within her own community also becomes strained, as her alliance with the disruptive humans leads to her being pursued by elven authorities who disapprove of her methods, particularly the forced stripping of other elves to search for spell fragments. Ultimately, Celsia evolves from a composed priestess whose single mistake sets a quest in motion into a perpetually flustered but resilient companion whose magical abilities and personal sacrifices are essential for any hope of resolving the crisis.