The Devil Is a Part-Timer, book 1
Satoshi Wagahara2015

Do you want fries with your hellfire? Being soundly thrashed by the hero Emilia, the Devil King and his general beat a hasty retreat to a parallel universe...only to land smack in the middle of bustling, modern-day Tokyo! Lacking the magic necessary to return home, the two are forced to assume human identities and live average human lives until they can find a better solution. And to make ends meet, Satan finds gainful employment at a nearby fast food joint! With his devilish mind set on working his way up the management food chain, what will become of his thirst for conquest?!