User blog comment:Sunako30/Who is your top five strongest characters in owari no seraph in your opinion/@comment-33177490-20160102170840/@comment-33177490-20160102233932

It's interesting because Mahiru she was originally a human before turning into a demon. After becoming a demon, she later went on and became a vampire and then turning into a demon yet again used by Guren.

Mahiru: Human > Demon > Vampire > Demon (as one of the Black Demon Series)

Sometimes I would get lost if it's Mahiru who was controlling Guren or is it his second personality that resurfaced.