Mayu Koharuno serves as the older sister to Silk Koharuno. She works professionally as a reporter, collaborating with journalist Yosaku Okamura. Mayu's role focuses on investigative activities aimed at uncovering the identities of the giant heroines protecting the city. In one documented instance, she spearheaded a surveillance operation at a beach setting, attempting to gather evidence that would reveal the heroines' true identities. This effort formed part of her relentless journalistic pursuit of the story surrounding the city's protectors.