Forced to flee his kingdom, Satan ends up in modern-day Tokyo with a feeble, virtually powerless, mortal body. Assuming the name of Sadao, he gets a job at McRonald's to survive while searching for a way to regain his evil magic. He later encounters and is pestered by the righteous hero Emila, who followed him to Earth but is almost powerless herself. Assuming the name of Emi, she's working as an office clerk while uncovering a way to regain her magic. Foes at first, they slowly become friends and allies as someone's trying to kill them using magic.