Marie is a student at Haré and Guu's jungle school and the younger sister of the perpetually sleepy teacher, Reiji-sensei. She habitually indulges in romantic fantasies and dramatic scenarios, imagining herself as a tragic, shōjo manga-esque character. Her initial friendship with Haré deepens into a romantic crush, growing more intense and occasionally aggressive over time. She experiences intense jealousy whenever Haré interacts with other females or visits the city, frequently envisioning him in romantic entanglements during his absences.

Due to her own lack of maternal upbringing, Marie harbors deep admiration for Haré's mother, Weda, actively seeking her maternal affection and validation, viewing her as a mother figure. She incorporates Dr. Clive into her idealized family fantasies as a paternal presence. Years after the main events, Marie marries Haré. They have a daughter whose mannerisms, including a characteristic smirk, echo Guu, suggesting a thematic connection to Guu's earlier departure and implied reincarnation.