High school student Nene Yashiro, desperate for a romantic miracle, makes a pact with the mischievous and powerful Hanako-kun, the ghostly guardian of the school’s supernatural secrets who resides in the girls’ bathroom. This decision thrusts her into a hidden world of mysterious wonders and dangerous apparitions known as "Yorishiro," forcing her to become Hanako-kun’s assistant. Together with her spectral friend and the hot-headed exorcist Kou Minamoto, Nene must navigate a series of eerie, often perilous supernatural phenomena while confronting the Seventh Mystery’s own mysterious past and the dark truths that bind him to the school. Blending whimsical comedy with heartfelt drama and atmospheric horror, the series explores themes of friendship, sacrifice, and the fragile boundary between the living and the dead. As Nene grows closer to her enigmatic companion, she uncovers the heartbreaking secrets behind his centuries-old curse and the true price of their contract.