Kyō Oogata is a male student in Chiyoko Kurotori's class at school. His most immediately noticeable trait is that he constantly carries a stuffed puppet on his left hand and speaks to it as though it were alive, giving him an eccentric and somewhat mysterious appearance to his classmates. Beneath this peculiar exterior, Kyō is a former student of the powerful demon known as Angolmois, and he possesses immense innate magical ability. His magic was sealed away by Angolmois directly into the stuffed puppet he wears, and he is usually seen with this seal in place. However, the seal is not perfect and occasionally breaks, allowing his power to leak through at unpredictable times. He is acutely aware of Chiyoko's secret life as a black witch in training, having correctly identified a magical charm root she discovered and having proven immune to the memory-erasing spells cast by the instructor Gyubid.

In terms of personality, Kyō comes across as an odd and quiet boy to many of his peers due to his habit of talking to his puppet. He speaks in a distinctive, drawn-out manner often ending phrases with a verbal tic akin to "dane". Underneath this quirky surface, he is calculating, ambitious, and aware of his own considerable strength. His primary motivation for much of the story is his desire to conquer the demon world, viewing the vast magical power sealed inside him as a means to claim that throne. Over time, his goals shift and he begins training as a first-class dark magic user, a path that takes priority over outright conquest. He also develops a deep and persistent personal interest in Chiyoko, whom he considers as his future wife. This sentiment is not reciprocated by Chiyoko, but he remains earnestly protective of her, going so far as to exclude her from certain sacrificial rituals due to his feelings.

Within the story, Kyō serves as a rival and occasional ally to Chiyoko. He is a major supporting figure whose secret magical background creates tension and conflict. His relationship with Angolmois is central to his character: the puppet that sealed his power is also his former master, and he coexists uneasily with it. A witch named Blossom takes on the identity of Kyō's younger sister, Momo Oogata, in order to live in his home and monitor the seal on his power, ensuring it stays in place. Among his classmates, Kyō's closeness to Chiyoko often draws jealousy from other boys such as Ryōtarō Asakura and Ashura Tōkaiji, who misunderstand the nature of their connection.

Kyō undergoes notable development as the narrative progresses. Initially introduced as a mysterious figure with hidden power, his background is gradually revealed, including his past as Angolmois's student and the circumstances of his sealing. A dedicated spin-off novel, Dark Prince Oogata Kyō, explores his early life in the fifth grade, his first awakening as a dark magic user, and his decision to aim for the throne of the demon world. Through these experiences, he evolves from a sealed antagonist into a more disciplined magic user actively working to control his abilities and pursue his own ambitions, all while maintaining his unusual personal mannerisms and his fixation on Chiyoko.

Regarding his notable abilities, Kyō wields extremely high-level magical power, strong enough that even his sealed form presents a significant threat. His potential is considered comparable to that of a high-ranking dark magic user or demon. He is able to recognize magical items and phenomena without difficulty, and his mind is resistant to certain spells, such as Gyubid's memory magic. The stuffed puppet not only contains his power but also serves as a protective charm, deflecting negative energy away from him and sometimes onto those nearby. When the seal is removed or weakened, his unrestrained magic can overwhelm opponents, reinforcing his status as one of the series' most powerful human characters.