When the app is launched, a ghost appears. Developed by four young adults, the app becomes the centerpiece of a livestream where they venture into a supposedly haunted mountain to prove its authenticity—only to meet a grim fate.

Bo-hee, a 14 year old boy, was raised by a single mother and has always thought his father had passed away. Bo-hee hears that his father may be alive, and he sets out in search for him with his best friend Nok-yang. He finds his half sister on the way and forms a friendship with her boyfriend.