Momo Ayase, a high school student who believes in spirits but doubts the existence of aliens, meets Ken Takakura, nicknamed Okarun, who believes exactly the opposite. To prove their theories, each agrees to investigate a place connected to the phenomenon they do not believe in. Their challenge quickly brings them face to face with very real supernatural and extraterrestrial forces, completely disrupting their everyday lives. Now connected to powers and threats they do not yet fully understand, Momo and Okarun face spirits, strange creatures, and visitors from beyond Earth while gradually forming a stronger bond.