The Devil Is a Part-Timer!, Vol. 23 (Manga)

A SUDDEN PROMOTION!With Lucifer defecting and Satan missing, Alciel unexpectedly finds himself in command of the Devil King's army. It may not be how he intended to take on the mantle, but he's more than ready to recoup their losses and lead them to victory! However, the Malebranche have a different end goal in mind-- one that will send Lucifer and Satan to face a never-before-seen enemy!