Nico

A fairy in the form of a long-haired gray cat. He dresses in clothes, walks on two legs, and pretends to be a gentleman. He is particular about his appearance and food. He extremely dislikes being treated as a cat, often saying, "I'm not a cat," but he loses strength when petted like a cat and is weak to catnip, showing that his habits are entirely those of a cat. Edgar often exploits these weaknesses, easily bribing him or sometimes petting his throat like a cat as a form of venting.

He was once the companion of Lydia's mother, Aurora. When Lydia was born, he promised Aurora to watch over her until she grew up. Although he considered returning to his homeland after Lydia's marriage, he decided to stay by her side due to Lydia's strong wish. He struggled alone with the secret of the bloodstone that Lydia had swallowed, but Raven encouraged him to confide in Lydia.

His abilities as a fairy are not particularly high, but he can make himself invisible and supports Lydia with his knowledge of fairies and the fairy world. His personality is carefree, and he has a somewhat unfeeling side, quickly fleeing and hiding when sensing danger. However, he cares deeply for Lydia and is more distressed than anyone else when she is in real danger. He also maintains a somewhat offbeat but amicable friendship with Raven.

Towards the end, he infiltrated the fairy world beneath the Tower of London to retrieve a fire agate. He was nearly killed by a wicked fairy doctor using Terran's body to steal his magic, but Alvin intervened just in time. He was transferred into the body of a kitten that had died being used by them. As a result, from just before the end of the main story, he appears as a black cat with short hair and white paws (a so-called "sock cat"), and Kelly adjusts his tie and other accessories to fit his new size.