The story: Flonne is an angel-in-training sent down from Celestia (Heaven) to the Netherworld (Hell) to assassinate the demon overlord. As the show begins, she finds a coffin with the young demon prince Laharl inside, who wakes soon after it's opened. It turns out his father the demon overlord is already dead. None too bothered by that, Laharl sets out to reclaim his throne. Flonne tags along, determined to teach Laharl the value of love. Soon they are joined by Etna, a female demon who commands an army of prennies (lost souls who resemble penguins.) It turns out a ten million bounty has been placed on Laharl's head, and now all sorts of demons are after him. The trio must also deal with a group from Earth who've arrived in their dimension-traveling ship: a man (the heroic and dramatic but brainless type,) a woman (a scantly-clad vixen,) and their robot.
I had a great time watching this series. I highly recommend it for anyone who loves fantasy-adventure-comedy anime.