名も無き鳥の飛ぶ夜明け Series by Hirotaka Kisaragi

Part of the angelic bureaucracy, Karasu is sent to earth to retrieve a demon living among humans. However, he's surprised to discover that Shirasagi only wants to throw away his heritage and his powers, and live as a human, and a holy human at that.

Karasu may have retrieved Shirasagi from the clutches of Beelzebub once, but Hell isn't quite ready to give up its claim just yet. However, the appearance of Koumori & Sarugami - a new ally & an old friend - may force our pair to not only acknowledge their debt to each other, but their true feelings as well.

Koumori leads Karasu and Shirasagi through the wastes of Purgatory, while high above, the Seraphim argue over how best to prevent the Distortion from spreading any further. When the war between Heaven and Hell begins once again, Dominions and Karasu restart their own fight, but soon the Archduke gets involved...and what happens in the end will take everyone by surprise! Faith, passion, and betrayal collide as the universe spirals downward towards chaos.. moreKoumori leads Karasu and Shirasagi through the wastes of Purgatory, while high above, the Seraphim argue over how best to prevent the Distortion from spreading any further. When the war between Heaven and Hell begins once again, Dominions and Karasu restart their own fight, but soon the Archduke gets involved...and what happens in the end will take everyone by surprise! Faith, passion, and betrayal collide as the universe spirals downward towards chaos... But are the feelings of two star-crossed lovers enough to set things right? less