The Devil is a Part-Timer Novel Volume 20 is written by Satoshi Wagahara and illustrated by 029 (Oniku).

Much like her younger sister Acieth, something strnage has started happening to Alas Ramus. To help their baby girl, Maou convinces the reluctant Emi to travel to her family's home in mystical...Eifukucho. There, the Demon King is floored by the luxurious furnishings like a proper alcove for the doorway, a full-sized refridgerator, and rooms big enough to actually spread out. He better get his bearings soon though, because this marks the start of him living under one roof with the Hero and their daughter!