"My My Mai" centers on Mai Kawasumi, a high school student who discovers she is the reincarnation of a powerful priestess from a mystical realm. This revelation comes to light when she encounters a mysterious boy named Yuu, who claims to be her guardian from the past. Yuu explains that Mai’s latent powers are essential to preventing the collapse of both the human world and the spiritual realm, which are interconnected through ancient rituals. As Mai begins to awaken her abilities, she is thrust into a conflict involving other reincarnated individuals, each with their own agendas and ties to the past.

The narrative unfolds as Mai navigates her dual identity, balancing her ordinary school life with the growing responsibilities of her priestess heritage. She forms alliances with other reincarnated beings, including Rin, a stoic warrior, and Aoi, a mischievous yet loyal companion. Together, they face off against antagonistic forces led by Kaito, a former ally of Mai’s past self who seeks to exploit her powers for his own gain. The story delves into themes of destiny, sacrifice, and the weight of past lives, as Mai struggles to reconcile her present self with the expectations of her past incarnation.

The plot is driven by a series of battles and rituals, each revealing more about the history of the spiritual realm and the roles Mai and her companions played in its downfall. Flashbacks provide insight into the relationships and betrayals that shaped the original priestess’s life, adding depth to the present-day conflicts. As the stakes escalate, Mai must confront her own fears and doubts, ultimately deciding whether to embrace her destiny or forge a new path. The series concludes with a climactic confrontation that determines the fate of both worlds, leaving room for reflection on the cyclical nature of history and the power of individual choice.