The demon who raised him, whom he called "grandfather" only now we find out, he actually is Ike's grandfather. Which is surprising because the freaking title of the series is "The Maou Army's Strongest Magician Was a Human"... only now we find out that he isn't human, but rather a human/demon halfbreed.
I mean the entire freaking foundational premise is the shock of a human being the demon armies strongest magician. But author decided this late in the game to change that. /facepalm
PS: I don't think that we've been told yet that his grandfather was the prior demon king. Rather, I thought that he was just a very strong magician.
