C-Could it be... the mythical isekai baby Japanese!?
As of chapter 450 in the WN (earlier, but that's where the English translation is at right now), Haruka questions this, and very slightly suspects it may be the case.
The baby, a male born into the world, was originally a 16 year old girl who had a terrible life, was abused, and was ultimately murdered in a back alley. I believe this was done because had it been a 16 year old boy, a lot of things they do/say would make little sense and/or be fairly creepy.
Haruka really needs to sit down for a day or two to get to know her own capabilities properly.
Good news, that starts to happen soon in the WN at this point in the story.
I will never understand that "not chasing after the bad guy" trope.
In the WN, Haruka actually launched a fireball at him as he escaped and just wasn't able to land a square hit. He flew away at high speed.
Also, Haruka should come clean with Corin. He doesn't have to tell her his whole back story about being an old man in a woman's body. But he should at least tell her that he's attracted to women; and that is the reason he leaves the room every time she gets naked to bath. She'll probably figure it out on her own in the future, just from his actions alone: consistently avoiding seeing her naked and total lack of romantic interest in men.
Haruka eventually does come clean with all of them, and they're all cool with it because they know Haruka would never do anything to compromise Collin.
I think you could very well be correct. Many middle-aged men in manga are depicted as quite perverted, so it's either a self-justification or just Haruka not really ever thinking about it. Haruka is Haruka, and in the end s/he has even from a very young age displayed that s/he doesn't, and never had any interest in romance or sexuality. That's definitely intentional, which is a cool touch by the author!
There is a good chance most manga authors have never even heard of the term before, never mind the concept. It's still a fairly recent introduction into western public conscious, and extremely niche in the world of manga. Slowly, though, things are changing!
I believe the manga already briefly brushed on this, but when Haruka was a teenage boy, he and a girl fell in love with each other. However, due to being too afraid to hurt her, he never showed his feelings towards her, and she broke up (in tears) with him over his lack of communication (she thought he didn't love her). He only began to recover from this during the scene with Al having to chase after her about staying in the party.
As for why that happened:
At a crucial moment in his life, Haruka asked his parents an important question about life (relationships in general, not strictly romantic ones) and they were having a bad day and gave a "don't bother asking anything like this" answer, causing him to socially recede for the rest of his life. Those parents died in an accident in his early 20s, so it's not like they had a chance to see he wasn't dating in his late 20s and ask why and fix their mistake before it was too late.
As far as the public conscious goes, I'm pretty sure asexuals have been known in the west (even the Roman republic-turned-empire) for over 2 millenia. Even earlier and in other places, too. They're just not part of any scandals, so they're not brought up with much enthusiasm.
Let me quote Jesus and the disciples from Matthew 19:10-12.
[The disciples said to Him, “If the relationship of the man with his wife is like this, it is better not to marry.” But He (Jesus) said to them, “Not all men can accept this statement, but only those to whom it has been given. For there are eunuchs who were born that way from their mother’s womb; and there are eunuchs who were made eunuchs by men; and there are also eunuchs who made themselves eunuchs for the sake of the kingdom of heaven. He who is able to accept this, let him accept it.”]
The context is that Jesus was originally talking about marriage and divorce, and hearing his answer to the pharisees, his disciples got a little scared of the commitment required in marriage, as Jesus was raising the bar compared to their culture's interpretation of the scriptures. Most of those disciples would eventually marry.
If you're wondering about what "made eunuchs by men" means, one common thing for any king or royalty with a harem to do was to have all male attendants of the harem castrated.
But, the born from the womb comment would cover asexual men, so the understanding of the concept is, as you can see, quite old.
