The Devil Is a Part-Timer!, Vol. 8 (Light Novel), Paperback/Satoshi Wagahara

For the Hero, whose mission is to slay the Devil King, Emilia Justina appears to have gone soft. She travels to Ente Isla with Alas Ramus to sort through her thoughts and investigate what's happened there since she went to Japan. The gang expects to see Emi again soon, but she never returnsMeanwhile, Maou (the Devil King) is studying for his driver's license, trying not to fret over the Hero's disappearance. On the way to his exam, he meets a strangely familiar pair...Could they know something about Emi?