Akujaku reidžó wa last boss datte kaeru hazu (E04)

Aileen finds out that Claude's aide, Keith Eigrid, has been selling demons. Keith tells Aileen about the reason why and reminisces about their past. Now that Aileen knows his true feelings, she decides to cooperate with Keith to prevent Claude from despairing about humanity and turning into a demon. At the same time, Cédric and Lilia visits the demon lord's castle to tell Claude Keith's secret?! (Crunchyroll)