In Spirit Circle, Fuuta Okeya, a 14-year-old with a unique birthmark, encounters Kouko Ishigami, a new classmate tied to a past marked by enmity. Despite a rocky start, their fateful connection leads to a revelation of shared history through reincarnations. As Fuuta delves into his past lives, he navigates a complex web of emotions and conflicts with Kouko, seeking to understand and perhaps alter their intertwined destinies.