Mineo Harumi holds the position of Treasurer in the Student Government at Misumaru Middle School. She appears quiet and demure, actively avoiding attention and typically concealing her emotions. Despite this reserved nature, she demonstrates notable resilience and approaches her duties with serious dedication. Her involvement in the mystery of the Shingu—a giant entity protecting Earth—is initially unspecified, though she is confirmed as a skilled fighter.

A significant connection exists between Harumi and Kyouichi Moriguchi, the passionate Student Vice President. While a mutual bond is present, neither openly acknowledges this relationship early on. Her understanding of Kyouichi's capabilities becomes critical during an alien attack on Tenmo town. Recognizing the essential nature of his previously underestimated psychic abilities, Harumi intervenes decisively. She removes him from school and clarifies that his power is vital for activating the Shingu's defenses, countering his belief in its insignificance. This action reveals her awareness of her peers' strengths and willingness to act in critical moments.

As a Student Government member, Harumi shares the responsibility of guarding the centuries-old secret of Earth's protection and the Shingu itself. This role aligns her with other council members possessing various psychic powers, though the specific nature or extent of her own potential abilities remains undetailed. Her consistent focus lies in supporting her peers and fulfilling her duties within this hidden framework.