Carbuncle is a magical creature and the familiar of the protagonist, Meg Raspberry. While the exact nature and origin of Carbuncle are not detailed in available sources, the character serves as a companion and caretaker to Meg. Carbuncle does not speak, but is highly expressive, using gestures and actions to communicate and react to the events unfolding around Meg.

The personality of Carbuncle is primarily defined by a dedicated and caring nature. As a familiar, Carbuncle is constantly by Meg’s side, looking after her and supporting her efforts. This role establishes Carbuncle as a key figure in the protagonist’s daily life, acting as a source of quiet stability. Physically, Carbuncle is described as having large ears and bearing a resemblance to a cross between a rabbit and a squirrel, presenting a small and likely endearing animal form. Carbuncle is not alone in this capacity, often found in the company of a snow-white owl named Shirofukurō, who is another magical creature associated with the main cast.

Within the story, Carbuncle’s primary function is to support Meg, who has been cursed and has only a year left to live. As Meg uses her magic to seek out tears of joy to save herself, Carbuncle remains a constant presence, looking after her as she faces the difficult year ahead. The available information does not contain details regarding Carbuncle’s personal motivations, specific magical abilities, background, relationships with other characters besides Meg, or any character development or changes throughout the narrative.