Hororo is one of the four main fairies who reside in the human world in their quest to learn about human customs and eventually become human themselves. She is specifically associated with the green bottle and personifies the season of winter. Her physical appearance is marked by long, straight black hair with a single strand of ahoge, or cowlick, often falling over her forehead, and she has distinctive green eyes.

Of the four fairies, Hororo has the quietest and most relaxed personality. She is frequently described as a natural airhead or a cloud cuckoo lander, as her mind tends to wander, and she often appears to be lost in thought or not fully listening to the conversations happening around her. Her thought process is notably slower than her companions, giving her a preoccupied and somewhat detached demeanor. This does not stem from a lack of intelligence but rather from her tendency to inhabit her own imaginative world. She may suddenly utter nonsensical or seemingly incomprehensible statements that the other fairies cannot quite follow, adding to her quirky and charming presence within the group. Despite her dreamy exterior, she is a dependable friend who offers her support when her companions truly need it.

Hororo possesses a notable love for food, with a particular fondness for egg tofu, and is characterized as a big eater. Her motivations are generally aligned with the group's primary goal of becoming human, though her approach is less driven than that of some of the others. She experiences the human world through her own unique, often whimsical, perspective, which includes indulging in fantasies such as playing the role of an evil scientist or creating absurd poetry.

Her role in the story is as a core member of the fairy quartet, each learning about a different aspect of human life. She shares a close bond with her fellow fairies Kururu, Chiriri, and Sarara, and their daily lives are filled with cheerful and often comedic interactions. Within the household, they are looked after by a human university student they all call Sensei-san. Hororo's feelings for Sensei-san are significant; she holds a deep affection for him that extends beyond a simple crush. This is demonstrated during events like Valentine's Day, where she and the other fairies attempt to express their feelings through gifts. Another key figure in her life is Oboro-chan, a winged cat. Hororo displays a particularly strong fascination with Oboro-chan's ability to float and is often seen quietly watching or gently interacting with him, suggesting a special fondness for the creature.

Over the course of the story, Hororo, like her friends, undergoes a period of growth and learning. As they experience a full year of seasons and human traditions, her initial dreamy confusion gives way to more concrete emotional expressions. In the end, although she does not fully achieve her goal of becoming human, she accepts the reality of her situation and graduates from the experience with a positive attitude, expressing sincere gratitude to Sensei-san for his guidance. In terms of abilities, as a fairy, she possesses magical powers, though her use of them is typically in service of trying to understand or replicate human activities, with results that often go awry in humorous ways. Her most notable "ability" is perhaps her immense appetite, particularly her capacity to consume large quantities of the food she loves.