Board Thread:General Discussion/@comment-24098614-20160522195522/@comment-25942629-20160530103731

There are actually quite a few vampires involved with the development of the Seraph of the End, and there are all of the Michaelas running around as well. We don't even know much about Michaelas yet (other than they have tasty blood), but it could be a big thing. We also haven't seen the strongest vampires fight seraphs yet. Additionally, he is more of a demon right now.

In order to kill him, they would actually have to find him. His group defected from the JIDA and is in hiding from them. They also don't want to kill their friend. Any JIDA member who knows he is a seraph would probably focus on capturing him instead, once his location is found.

For the most part, they seem to be focused on subdoing vampires instead of hunting down a few defectors. Although Guren knows Yu is a seraph, the JIDA as a whole does not.

They kill demons to prevent their other soldiers from being wiped out, but Yu is not a part of their soldiers anymore.

Sorry. That was a lot of rambling for just saying they cannot kill what they cannot find. They would only kill demons in their army, not on the outside either.