Forty years ago, monster-filled towers appeared, unleashing chaos across the world. Heroes, empowered by spirits, rose to combat the beasts. Jaeha Min, a soldier turned civilian investigator, dreams of becoming one of these heroes despite his low aptitude. Everything changes when he accidentally bonds with the spirit of the Heavenly Demon. Now with a powerful mentor inside him, Jaeha embarks on a journey to master his newfound abilities and help the demon return home.