Sugar is a nine-year-old snow fairy apprentice from the fairy world. Her core aspiration is to become a full season fairy like her mother, famed for crafting snow that feels soft and warm and fosters cherished memories. To achieve this, she must complete training in the human world by finding an undefined "Twinkle" to make her magic flower bloom, a crucial step in her fairy maturation.

Standing four inches tall, Sugar has pink hair that can appear blond in certain lights and expressive eyes described as purple, brown, or purplish-blue. She wears a fluffy white dress with a snow rabbit motif, featuring a purple bow and a rabbit-tail cotton ball. Her outfit includes matching booties adorned with snowflakes, a snowflake choker necklace, and a bonnet accented with green grass. She carries a snow rabbit-shaped purse, a hammerspace holding items like her magical piccolo—a light blue instrument with purple accents and pink keys that emits sparkles when played.

Sugar blends playful impulsivity with earnest determination. She exhibits toddler-like enthusiasm, often acting before thinking and causing accidental disruptions. She expresses affection by kissing people or objects, particularly unnerving her friend Salt. Her speech includes the catchphrase "Waffo!", a mispronunciation stemming from her love of waffles discovered after Saga revived her from starvation. Despite her clumsiness, she shows fierce loyalty and protectiveness toward friends and moments of seriousness about her duties. Setbacks, like losing her magic seed or fearing Saga's rejection, reveal her emotional vulnerability.

Her story starts in Muhlenburg, Germany, arriving weakened by hunger until Saga feeds her, forging their bond. Sugar moves into Saga's room, disrupting her meticulously scheduled life. She accompanies Saga to school, misunderstands human social norms, and mistakenly identifies objects like a classmate's ring as "Twinkles." Her magic practice often causes minor chaos, like unintended snowfall. A critical conflict arises when she loses her vital magic seed; it later sprouts in Saga’s room, tethering Sugar to the location.

During her training, she is joined by fellow apprentices Salt, a sun fairy, and Pepper, a wind fairy. Their dynamics highlight her social nature; her attempts to kiss Salt suggest a one-sided crush despite his protests. Sugar learns accountability, such as apologizing after damaging Saga’s treasured sheet music, a keepsake from Saga’s deceased mother. In the manga, her magic flower withers, reverting her to an egg form. Saga mobilizes classmates to find Twinkles, reviving Sugar and creating a final snowfall before Sugar's departure. In the anime, the flower blooms successfully, but Sugar hesitates to leave Saga. Both narratives conclude with Sugar achieving full fairy status, requiring her return to the fairy world and the loss of Saga’s ability to see her, though subtle hints suggest Sugar remains nearby.

Her character development intertwines with Saga’s; their friendship challenges Saga’s rigidity while teaching Sugar responsibility. The unresolved nature of "Twinkles"—implied to represent human joy or cherished moments—underscores her thematic role in emphasizing emotional connections over structured pursuits.