When he picks both babies up, he notes the crests but he states them as a "coincidence", then takes both of them to live with him in his village. He even says that the fact that everyone is searching for them "doesn't matter to this remote village". This all happens in the first chapter. Then on the second chapter Lusha states "dad told me to keep it hidden so people doesn't get the wrong idea", the girl who has massive awareness of everything going around and has developed her mind far beyond what an 8 years old could possibly achieve. The demons are running wild looking for the demon lord and he never thinks "perhaps it has something to do with Luna". Then the old man states in a thought "I don't know why but demons don't attack Luna, some like her (like the dog), and the rest avoid her", then the fairies tell him "Release the hero", he once again doesn't get a clue of why they're saying that, after all the fairies go around Lusha's crest hand. Then he sees an 8 year old girl using dark magic, he even states it's the most compatible with demons, and even if some humans can use it, he only met one, only one, one of the strongest and most popular adventurers states that his daughter can use one of the hardest types of magic, while having the demon lord crest, and right after that he asks if she wants to be a royal mage, if you know she's the demon lord why in tarnation would you ask her if she wants to be a royal mage for a human kingdom, COME ON, it's throwing herself into the fangs of the wolf. She smartly replies it'll be a disaster and he's surprised by it and doesn't seem to acknowledge the fact that she knows her real identity, once again. Then he gets attacked by a group named the "Hero's Cult", and once again he shows his obliviousness to the situation by saying "those kids have special powers" and going full in with "who knows what will they do if they believe that Lusha is the Hero", not "know that she is the Hero", "believe". He's thinking, why would he think that way if the knew that she was the hero, there is nobody else to convince of the opposite for goodness sake.
This man is the epitome of retarded lawfulness, I'd even argue that he might even allow or be convinced by someone to let his daughters go fullfill their roles but they'll say "we don't want to, we want to be with you", or he'll say "no way, you can't be the Hero and the Demon Lord!!!1!!11" when his daughters tell him who they are.
I also want to add that one most powerful and experienced adventurers got done by powder that must be breathed in... Not by sleeping magic, no, that'd be too reasonable, he willingly breathed it in instead of holding his breath even though he knew what it was.
So, no, at any point so far in this story it was stated or shown that this man knows who his daughters are, in fact, it's the absolute opposite. Of course, unless the author goes full Heeeeell to the nono and shows us that the old man is actually a 10 billion IQ genius and says "This was all in my plan", all the clearly valid points above are no longer valid and I drop this for having such a terrible storytelling and development.
I fear this might turn into a "Save Private Luna form the Demon army to live our peaceful village slow life" at this rate.
I think the worst part of this manga, aside from the clear obliviousness of this man and the terrible combat art (because that centaur fight was horrendous in every way) is the fact that most of the "powerful" beings can't think for themselves. Take the Fairy queen for example, she has a stick so high up her butt that she wants to wage war, I get, it's what has always happened with the Hero and Demon Lord, yet she doesn't even try to gather info on the autistic man and their lifestyles, Lusha states clear, logical and strong points on her statement, but the queen just thinks the worst of the dude and tries to kidnap the girl. She never even once tries to think, "yeah, perhaps war can be avoided, the Hero and Demon Lord themselves are showing us that humans and demons can in fact get along, they even consider each other as sister". Asking them to think on an alternative would be too much for their peanut sized brains.
C'mon, having to turn off your brain to enjoy something that is attempting to be serious is ridiculous.
