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.
It won't return to its scabbard 
until its enemy stops breathing.
Es kehrt nicht in die Scheide zurück,
solange sein Feind nicht erschlagen ist.
No volverá a su vaina hasta
que el enemigo deje de respirar.
No volverá a su vaina hasta
que el enemigo deje de respirar.
Elle ne retourne dans son fourreau
qu’une fois son ennemi tué.
Essa non può tornare nel fodero
senza aver ucciso il suo nemico.
Ela não retorna à sua bainha 
até o inimigo parar de respirar.
Он не вернётся в ножны, 
пока его враг не испустит последний вздох.