@sssr
So it's not a case of Miko having special vision but a case of something obscuring people's senses when the supernatural happens.
...I hate to break this to you, but in both folklore and religion - inside Japan and in the west - this isn't the case. And the fact that there's billions of people on this world and very, very, very few claim to be able to see them (in the manga's universe and our own real life) shows that, yes, it's a case of having something special that allows you to see them. Same way how people that have synesthesia see shit you and I don't see and how people with colorblindness might not be able to make out colors normally, but what they can see is so well defined that companies like Kodak hired people with specific colorblindness to check for color correction accuracy.
And it's funny you mention "a veil," because according to my Irish grandaunt (who was born in the old country and emigrated here as a small child with my grandmother and... well... spooked me and the rest of the family often enough that we all thought she a tinge of it herself - she knew shit that people shouldn't have any earthly reason to know) a child born with "a veil" (a veiled birth, a caul) were ones that would likely have such gifts/powers. I.E. born with something special. The only reason Miko can see and hear shit that's been recorded in some way is because she has that power to see something that is not normally visible by humans or scientific equipment.
And it makes sense, if true. Because we can compare scientific testing with human condition observation. Humans see in the ~400-700nm wavelength range (and, yes, this does vary between person-to-person very slightly, but not enough to really matter). We don't see shit. We go to the scientific equipment measuring changes or movement in the ~400-700nm range. It, too, doesn't see shit. You brought up visible light, but think on this: there are billions upon billions of people in this world with billions of cameras. Yet look at how little evidence we have in the way of people seeing things we shouldn't be seeing. And look at how much that percentage of "weird shit" increases when you start looking into non-visible light and other things.
So, no, visible light is off the table. Art Bell liked to talk at length about shadow people. You might have even seen them yourself. I have. You see a human shape or shadow that looks like someone is standing there out of the corner of your eye and you turn to look and there's nothing there or you have a brief afterimage/glow. Art Bell made the same point - they don't show up in photography, but the phenomena was becoming more and more widespread. His theory was electromagnetic spectrum frequency. Specifically, he theorized, TVs and monitors which were becoming more and more common. And the refresh rate of those devices (like, say, 60Hz) allowing our eyes to focus or have something we normally can't see reflected. Is it real? Is that what's causing it? I dunno, but the theory is sound if you assume that something is actually there. Reminds me of one short story where a guy invented a new camera that could slow and speed up footage at will and started seeing horrific and weird shit that normally couldn't be seen because of the frequency it operated at.
There's a lot of shit we don't know yet. Dark energy and dark matter are... enigmas. We only know that such things exist because we can see that from what we can't see there isn't enough matter holding some galaxies together, so something else has to fit. And the implications of string theory and quantium mechanics where we start dealing with mind-numbing shit like multiple dimensions and observer-interaction/wave function collapse where you can be asked "is that moving or is it stationary" and answer with "yes" and be correct on both accounts.
...But I think we can stop looking at regular visible light and smartphone cameras, because statistically we should already be seeing a mountain of unexplained weird shit by now.