The way Iruma eats so much it'll bankrupt the border police.
I also think that maybe Naberius Narnia in his twisted logic wants to get rid of Iruma by deporting him to the human world to save him and so that Iruma doesn't end up on his father's experiment table.
And I think that the place where Baal improved Atori and experimented on Behemolt is actually the Sanzu laboratory, which Baal inherited from Nightwalker. Or I think Baal works for the crazy Nightwalker.
And Nightwalker being in a wheelchair. I wonder out of curiosity how Nightwalker would have ended up in a wheelchair. But just like Dr. Cart Connors wanted to regrow his amputated arm and injected himself with lizard DNA or how Dr. Michael Morbius, a rare and serious blood disease (hemophilia and aplastic anemia) thought of curing himself through bats.
I'm thinking of the version/theory in which the interim demon king Kushinashi was killed by Naberius Nightwalker. And if Uncle Naberius, who many compare to Lewin Light from Blue Exorcist, was also a member of the 13 crowns when Derkila was the demon king. Maybe Kushinashi asked for help from Uncle Naberius again, and she said that someone wanted to kill her. And Uncle Naberius didn't kill his brother Nightwalker and in fact, through some kind of luck that Nightwalker had, he ended up being left disabled.
The idea is that Kushinashi is dead, being Kiriwo's childhood friend, saying that she received that hair accessory from her deceased grandmother. That accessory that Kiriwo's childhood friend wore is identical to the hair accessory that Kushinashi also wore.