User blog comment:Sunako30/ Who do you think is the main antagonist of Owari no seraph/@comment-67.5.230.127-20160122043712/@comment-25942629-20160123140439

Kureto is really arrogant and desperate. If he doesn't try that, then he believes the human race is doomed. This was a desperate do-or-die move of his. He's actually rather cautious when compared to many of the other powerful characters. We don't know how many seraphs have come and gone prior to this timeline in the manga. Since the seas are poisoned, it looks like the third trumpet already had some action. Since 90% of the human population was killed off at the onset, its possible that other seraph have already come and gone.

Of course, if people weren't messing experimenting with angels, then the Apocalypse might not have happened in the first place...

Humans stand a much better chance of survival if vampires are distracted by a third side. However, it looks like Mahiru manipulated things from the start to lure all of the strongest vampires to Japan. Depending on how things turn out, it's possible that she and Guren may end up taking rule over the humans or accomplishing whatever objective she's aiming for. Krul helped her out quite a bit by letting the humans' experimentation get this far. Since Mahiru is now a demon, it's possible that her objective might be to destroy the world. The weird thing is that she and Guren intentionally gave Yu a powerful demon. Thanks to that, Asuramaru was able to keep the angel part of him in check, and he has fallen from an angel into a demon. In that case, perhaps she is aiming to have demons rule the world instead? Make Hell on Earth or something.