The devil is a part-timer!, vol. 3 (light novel), paperback/satoshi wagahara

Do you want fries with your hellfire? A portal opens in the courtyard of the Devils Castle (a tiny walk-up).

From it emerges a little girl who calls the Devil King papa and the Hero mama.

Ashiya and Chiho are shocked to discover that Maou and Emi had that kind of relationship, but nobodys more surprised than the two new parents.

Will Maou the breadwinner be able to make the grade when it comes to child rearing? And will this spell the end of the starry-eyed Emis romantic ambitions?.