User blog comment:Crimson Marauder/Origin of Vampires???/@comment-25942629-20151218150038/@comment-25942629-20160105003434

We don't know who rules Europe. Lest only said he destroyed the spell casting organization there, not that he ruled the entire continent. I don't know that he'd be so hasty to come and take over Japan if he were already a king elsewhere.

Krul and Lest seemed to be talking about physical strength since she asked him if he were picking a fight. The also specified that he was 200 younger and would typically be expected to be the weaker one.

In the Catastrophe LN, it looks like Mahiru specifies that the humans will destroy the world "again," so you might not be off the mark. However, Seraph does not take things completely literally with religious reference and has changed things a little. For example, the Michaela LN specifies Michaela as a female name and not the masculine form of Michael.