Hiroshi Iidabashi, often referred to as Hakase Iidabashi due to his intellect, is a central character in the story who serves as the bespectacled best friend and fellow detective to the more flamboyant Eiichiro Yotsuya. He is a high school classmate of Yotsuya and works alongside him in their detective agency. Iidabashi is characterized by his sensible and level-headed personality, which often places him in the role of the straight man to Yotsuya's greedy and outlandish schemes. Despite his generally calm demeanor, he is not afraid to lose his temper, frequently yelling at Nanako when he believes she has done something wrong, though this harshness is not born from malice.

His primary motivation is tied to his genuine affection for Nanako, the super-powered girl at the center of the agency's activities. He secretly harbors a deep crush on her, a fact that creates a dynamic of unrequited love as Nanako herself is infatuated with Yotsuya. While Yotsuya sees Nanako primarily as a tool to make money and advance the agency's reputation, Iidabashi is portrayed as having a kinder heart, genuinely caring for the girl's well-being even as he goes along with his friend's plans. He is an aspiring manga artist, a dream that reflects his creative and somewhat more earnest nature compared to his partner.

In the story, Iidabashi acts as a crucial foil to Yotsuya, grounding the duo's more outlandish ideas with his practical sense. His key relationships are with Yotsuya and Nanako. The partnership with Yotsuya is a comedic duo, with Iidabashi often serving as the unwilling guinea pig for Yotsuya's latest experiments and inventions. His relationship with Nanako is more tender, marked by his unspoken feelings and his role as a sometimes stern but ultimately caring companion.

Throughout the series, his role remains largely consistent as part of the main comedic trio, providing a sense of normalcy and frustrated sensibility amidst the chaotic situations caused by Nanako's powers and the parade of bizarre villains. A notable aspect of his character is his willingness to be the test subject for Yotsuya's various gadgets, demonstrating a mix of loyalty and weakness in the face of his friend's forceful personality. One of his most significant character traits is his unrequited love for Nanako, a central emotional thread that highlights his more sincere and vulnerable side in contrast to the more self-serving motives of those around him. While the series does not focus on extensive personal development for Iidabashi, his dynamic with the other two main characters forms the comedic and emotional core of the story.