The Devil is a Part-Timer Novel Volume 9 is written by Satoshi Wagahara and illustrated by 029 (Oniku).

When Emilia the Hero is in danger, she finds an unlikely ally in The Devil King! Unfortunately, with Ashiya kidnapped by Gabriel, the team is seriously lacking in manpower. Maou and Suzuno team up, traveling undercover through Ente Isla on a rescue mission, and a mysterious girl claiming to be Alas Ramus's younger sister tags along. Meanwhile, Emi and Alas Ramus get caught up in the middle of Olba's schemes. The sides among angels, demons, and humans--and who's good and who's evil--come crashing down!