He, for most of the series, operated as Kamen Rider TheBee, acquiring the TheBee Zecter after Kagami relinquished it. Prior to it, Kageyama was originally under Yaguruma's command and a good friend of his, believing deeply in his superior's philosophy of teamwork and "Perfect Harmony". After TheBee Zecter rejected Yaguruma and chose Kagami, Kageyama attempted to make Kagami understand his new responsibilities. He was baffled when Kagami rejected TheBee Zecter in favor of his friendship with Tendou, whom he developed a grudge against.