Considering I only started this manga a few weeks ago, I'm really glad to have read it.
It's one of the few Mangas I'd rate 10/10 and the best comedy focused manga I've read so far, but that's mostly because it's also amazing in all the other genre aspects it includes.
I could totally see Haru being Nittas and Hitomis son from the future, but isn't there the possibilty that the future where they end up together has been prevented by their previous actions? The other ESPer girls are still around too, even though their future and existence should be prevented by now, so even if Haru is the Nittomi child, their future may never come to pass at this point.