Kiyotsugu Kiyojūji is a middle school student and a classmate of the series' protagonist, Rikuo Nura, serving as the founder and president of the Kiyojūji Paranormal Investigation Squad, also known as the Kiyo Cross Squad. As the son of a wealthy and influential family, he has access to significant resources, including a wide network of contacts and secondary family homes in various parts of Japan, which he often uses to facilitate his investigations.

His background features a dramatic reversal of beliefs. In his younger days, Kiyotsugu was a skeptic who actively discredited the existence of yōkai, even teasing Rikuo and presenting research that he claimed disproved their existence. This changed completely roughly four years before the main story when he was rescued from a bus accident by Rikuo’s nocturnal yōkai form, the "Lord of Pandemonium". This encounter transformed him into a fervent yōkai enthusiast, driven by a desire to prove their existence and a desperate hope to meet his mysterious savior again.

Personality-wise, Kiyotsugu is known for his bombastic and forceful nature, often dragging his reluctant classmates into yōkai hunts and themed games regardless of their interest. He has a grandiose and theatrical manner of speaking and is easily taken in by anything related to yōkai, such as purchasing a supposed exorcist's sword online. His obsession is so pronounced that he has even expressed a wish to be kidnapped by a yōkai. A recurring comedic element in the series is that despite his passionate pursuit of the supernatural, he nearly always narrowly misses direct encounters with real yōkai, with his most significant experiences being the initial rescue and later events during major conflicts.

Kiyotsugu's primary motivation is to prove the existence of yōkai and to encounter the Lord of Pandemonium who saved him. He acts as the driving force behind his investigation squad, leading his friends, including the human Rikuo and the disguised yōkai like Tsurara and Aotabō, on excursions to find evidence. He serves a crucial role as a human link to the supernatural world, often providing information and organizing the group's activities. His faith is severely tested when a rumor spreads that Rikuo is a dangerous yōkai responsible for chaos, but his response is to resolve to prove his friend’s innocence and reveal the truth. He also runs for and wins the position of student council president after a real yōkai attack is mistaken for one of his theatrical performances.

His key relationship is with Rikuo Nura. Ironically, Kiyotsugu’s childhood ridicule of Rikuo’s connection to yōkai caused Rikuo to start hiding his non-human nature, making the rescue a pivotal moment for both of them. Once Kiyotsugu learns the truth about Rikuo, he remains a loyal friend who actively works to clear his name. He also has close ties with his fellow squad members, including Shima, Kana, and the onmyōji Yura Keikain.

Kiyotsugu’s development is marked by his transition from a skeptic to an obsessive believer and finally to a proactive human ally who uses his unique skills to support his yōkai friends. In the Demon Capital arc, he demonstrates this growth by traveling to Kyoto with the investigation squad and seeking shelter with Yura Keikain’s family, placing himself directly in the path of major supernatural conflicts.

Despite his lack of combat ability, Kiyotsugu has several notable non-combat abilities. He possesses extensive knowledge of yōkai legends, stories, and weaknesses. He is also a skilled computer interface expert, having created and maintained a website called "Yōkai Knowledge" where people can report sightings and which ironically often provides data that coincides with real supernatural events. Furthermore, he can leverage his family's wealth to fund investigations, secure accommodations, and even create specialty items like a yōkai doll with a built-in cellphone.