A nerd must fight powerful spirits and aliens all vying for the secret power of his “family jewel,” so who better to fight alongside him than his high school crush and a spirit granny?! Okarun and the gang are off to a hot springs town to investigate the mystery of Jiji’s family. But when they get there, a strange family in cahoots with the police starts causing trouble for them, and before Okarun and the others can get to the bottom of the mystery, Momo ends up as an offering to the local god!