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.
Yes, the seven demon lords that 
preside over the demons of Hell.
Ja, die sieben Dämonenherren,
die über die anderen Dämonen der Hölle stehen.
Sí. Los siete demonios que gobiernan
a los demás en el Infierno.
Sí. Los siete demonios que gobiernan
a los demás en el Infierno.
Esatto, le sette Potenze Demoniache
che amministrano i demoni dell'Inferno.
Sim, esses são os demônios que regem 
sobre os outros demônios do Inferno.
Да. Верховные демоны, 
которые правят всеми в аду.