Meido no Koi wa Enma Shidai!

Tomari, a low-level administration worker in Hell, has suddenly been appointed to Enma Hall to be the aide to the King of Hell himself. There, she finds that she will have her hands full, and the King of Hell will keep her real busy, but not in the manner that she initially thought... What's worse, she didn't know what she literally signed up for, courtesy of the King. A contract love comedy unfolds!

(Source: MangaDex)

Included one-shot:
Volume 6: Jigoku no Sata wa Joushi Shidai