Hazuki Shiberia, one of Uiba Shikatani's childhood friends, is a first-year junior high student older than Uiba herself. As the daughter of a dry goods store owner, she bears the nickname "Moon Sister," used by Uiba and their peers. Hazuki bursts with energy and possesses notable physical strength. Her combative nature surfaces readily when challenged, particularly driving her to consistently avenge the character Kawata.

Exploring a mysterious island ignited Hazuki's curiosity about exotic creatures and plants. She actively studies the various animals encountered, displaying a special fascination for rare species, an interest that sometimes leads her into perilous situations. Within the group, Hazuki contributes significantly to problem-solving, frequently devising creative solutions using her intelligence and resourcefulness. Her quick thinking consistently assists her friends in overcoming obstacles throughout their explorations.

Her foundational bond with Uiba remains central to her interactions, sustained by their shared childhood experiences. Hazuki's background as part of a merchant family and her established friendships shape her supportive role within the group dynamics.