The Devil Is a Part-Timer!, Vol. 9 (Manga)

The hero/office worker Emi is stuck back in Ente Isla, while devil king/part-timer Maou needs to rescue his lieutenant Ashiya from the archangel Gabriel! As Emi researches what happened to her father, she discovers an incredible secret. Just who is Emi's mother, and why is her identity tied to the fate of the world itself...?