Laharl wakes from a two-year coma in his coffin to find his vassal Etna standing over him flanked by weapons. His father, King Krichevskoy, died while he slept. Laharl sets out immediately to reclaim the Netherworld throne, starting with a raid on the castle of the self-styled "Dark Adonis" Vyers — renamed "Mid-Boss" on the spot.
There he meets Flonne, an Angel Trainee dispatched by Seraph Lamington to assassinate the already-dead king. Fascinated by Laharl's complete absence of grief, Flonne joins the party to investigate whether demons can feel love. Watching from the shadows: the paranoid Archangel Vulcanus, who misreads Flonne's presence as treason.
Etna demands Laharl pay the Prinnies' wages, triggering an attack on the wealthy demon Hoggmeiser. Flonne convinces Laharl to spare him when Hoggmeiser's son intervenes; Hoggmeiser joins the party. A compromising photograph is then used to blackmail Laharl into a fight for overlordship against the vampire Maderas — exiled by Krichevskoy for stealing his favorite black pretzels. Maderas had been controlling Etna by holding her memory hostage, instructing her to kill Laharl; she poisoned him to sleep instead. Etna turns on Maderas, and he falls.
One night, Flonne discovers Prinnies chanting and leaving the castle. Chasing them down, Laharl encounters Death himself, who reveals that Big Sis Prinny is Laharl's own mother — she became a Prinny by sacrificing her life to save his.