User blog comment:Carol of the bells/Updates/@comment-26328778-20150912071105

I say that some other being attacked their mom, maybe by ossessing Zen, Ko tried to kill it, but the mother protected Zen, who may have been possesed, and was killed by Ko. The thingy then possessed Hisagi (I have no idea how) and then events proceeded as we learned... maybe...

This is my theory :P