Kelpie

A fairy from Lydia's past. Though he has a tyrannical personality, he is kind to Lydia. He chased her all the way to London to bring her back to Scotland and has stayed around her ever since. In front of people, he appears as a tall, handsome young man with black curly hair, but his true form is a ferocious water horse that lures humans with his beauty and demonic eyes, dragging them to the bottom of the water and eating everything except their liver. "Kelpie" is a term for water horses, and he does not have a personal name.

Water horses are a type of malevolent fairy (Unseelie Court) and generally see humans as food. However, after an incident involving his younger brother falling in love with a human, he met Lydia, who did not fear him as a water horse and saw him for who he was rather than his species. He grew fond of Lydia, wishing to live with her and repeatedly proposing to her despite being rejected. He remains around her without concern.

He prioritizes Lydia's safety above all else, often rushing to her aid in times of danger. However, he has little interest in other humans and will not hesitate to abandon them if they are around. He acknowledges Lydia as the "first Fairy Doctor to have tamed a water horse," and this stance has not changed even after her marriage. Despite knowing that Edgar has inherited the title of Prince, he respects Lydia's wishes and does not oppose their marriage.

Recently, he has been concerned about Ermine, who is often forced to fight alone due to her position, and frequently appears before her to save her from danger or offer advice. He also granted her final wish after she found the Fire Agate.

Even after Lydia gave birth, he continues to live near her. Although Alvin, who has grown to five years old, is somewhat afraid of him, he still shows his caring nature.