Totsuka Maria was praying in a chapel at Seiseki Girls' Academy when a black cross comes falling from the sky. On that cross, was a fallen angel, bearing the sin of pride, Lucifer. Maria attempt to tend to the angel, but the floor falls out and she disappears. Lucifer finds herself in the depths of hell, and runs into the Demon Lord of Envy, Leviathan.
I'm one of the Seven Mortal Sins, 
the Demon Lord of Envy, Leviathan!
Ich bin eine der sieben Todsünden,
Dämonenherrin des Neids, Leviathan!
¡Uno de los Siete Pecados Capitales,
el Demonio de la Envidia, Leviatán!
¡Uno de los Siete Pecados Capitales,
el Demonio de la Envidia, Leviatán!
Je suis Léviathan, démon de l’envie,
l’un des sept péchés capitaux.
Mi presento, sono uno dei Sette Vizi Capitali,
il Demone dell'Invidia, Leviathan!
Eu sou um dos Sete Pecados Capitais,
 o Demônio da Inveja, Leviathan!
Я одна из семи смертных грехов — 
Воплощение Зависти — Левиафан.