The Dirty Way to Destroy Goddess's Heroes, Vol. 5 (light novel): Seeds of Normalcy

After escaping the Goddess's attacks by going deep into the Demon World, Shinichi is desperate to find a way to counterattack. But even when he scans the ancient texts to get a leg up on her, he doesn't come up with any leads. That's when he finds where the red dragon has been slumbering all this time. In this climactic volume, Shinichi realizes he needs to act now—if he wants a shot at taking the Goddess down for good!