Momo Ayase is a high school girl who is convinced that ghosts exist but doesn't believe in aliens. On the other hand, her classmate Ken Takakura, whom Momo affectionately calls "Okarun," is a firm believer in aliens but dismisses the idea of ghosts. To settle their differences, they make a bet: each will visit places linked to the phenomena they believe in—Momo will explore alien-related sites, while Okarun will investigate locations tied to the supernatural.