Maruru is Hanamaru's younger sister, living in Guru Guru Town with him and their parents as part of a generous immediate family. She exhibits emotional expressiveness, particularly a tendency for dramatic and inelegant blubbering when crying, which distinguishes her within group dynamics.

Her portrayal frequently involves sibling interactions, including conflicts with Hanamaru. These quarrels, sometimes contentious but quickly resolved, reflect typical childhood disagreements; one instance documents Hanamaru temporarily rejecting the idea of having a sister during an emotional dispute. Age-appropriate activities, like playing with a tricycle, represent her interests. She interacts with Hanamaru's friends, though specific individual relationships beyond her family are not detailed. Her documented background and character traits remain confined to these familial relationships, behaviors, and minor everyday occurrences within the series' episodic structure.