"Kamogawa Horumo" centers around Kyoto University freshman Akira Abe, who joins the seemingly ordinary club "Kyoto University Azure Dragons" to meet girls. However, he soon discovers the club is anything but ordinary. The members are involved in a centuries-old battle game called "Horumo," where they command small spirit creatures known as "Oni" to compete against rival teams. These Oni are invisible to ordinary humans and are summoned and controlled through chants and rituals.

The game of Horumo is governed by strict rules, with teams battling to capture each other's Oni. The stakes are high, as losing all Oni results in severe consequences, including memory loss or even death. Akira, initially reluctant and clueless, is thrust into this supernatural world alongside his clubmates, including the enigmatic and skilled leader Kyoko Kamo, the stoic Ryuuji Sakaguchi, and the cheerful but competitive Mitsuru Kawabata. As Akira learns the intricacies of Horumo, he begins to uncover the deeper mysteries surrounding the game, its origins, and its connection to ancient Japanese mythology.

The narrative explores the dynamics of teamwork, strategy, and personal growth as Akira and his friends face increasingly challenging opponents. The story balances supernatural battles with slice-of-life elements, delving into the characters' relationships and personal struggles. Themes of loyalty, friendship, and self-discovery are woven into the plot as the characters navigate the pressures of both university life and the high-stakes world of Horumo. The series combines humor, action, and a touch of romance, creating a unique blend of genres that keeps the narrative engaging and unpredictable.