Nico is a fairy from the anime Earl and Fairy who takes the appearance of a fluffy, gray, long-haired cat. He walks on two legs like a human, though he is capable of moving on all fours, and he wears clothing, most often a neck ribbon but sometimes suits or tailcoats. He insists that he is not a cat and becomes irritated when treated as one.

Nico has a refined and gentlemanly personality. He is particular about his appearance, taking great care of his fur, whiskers, and attire. He enjoys liquor and fine tea. Despite his dignified demeanor, he is somewhat cowardly and tends to vanish when situations become dangerous, as he is unwilling or unable to engage in physical combat. Edgar sometimes provokes him on purpose by petting or scratching him like an ordinary cat, which Nico resents.

Nico was originally the companion of Lydia's mother before becoming Lydia's own guide and partner. He serves as a trusted advisor to Lydia, helping her navigate the fairy world and gathering information from other fairies in the area. He can turn invisible and is literate in human languages, allowing him to read and write. His guidance is invaluable to Lydia, even though he avoids direct confrontation. Edgar occasionally bribes Nico with fine food or gentlemanly accessories such as a cane or tailcoat to learn about Lydia's thoughts and activities.

Nico's relationship with Lydia is one of long-standing loyalty and mutual reliance, built on his history with her family and his ongoing role as her fairy companion. He shares a more teasing dynamic with Edgar, who exploits Nico's vanity and love of comforts to gain information. Over the course of the story, Nico remains a steadfast presence, using his knowledge of the fairy realm and his abilities to support Lydia in her adventures.