Dandadan. Volume 5: Yukinobu Tatsu

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?!
Momo Ayase and Okarun are on opposite sides of the paranormal spectrum regarding what they’ll believe in and what they won’t. Their quest to prove each other wrong leads them down a path of secret crushes and paranormal battles they’ll have to participate in to believe!
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!