From what I can see, Nanami can copy/read Sigurd's fighting style perfectly so he loses his usual skill advantage. What she cannot do is copy his physicals, which are nearly x4 her own, or his runes since they are not a physical/anatomical characteristic.
If she didn't have her dura negation, I'd call stomp but as it stands, voting Sigurd for versatility, range, AP and hax.
While we are on the topic of runes, I just remembered that even if she can copy them, Sigurd resists their effects with his magic resist anyway which still leaves the fight heavily in his favor regardless.
Ninpo has been shown to do some bizarre things, and is essentially the closest thing the series has to magic (aside from Shikizaki's expertise in occult rituals and soothsaying abilities)
There even exists a Ninpo that allowed a man/woman to become literally nothing but an immortal, intangible spirit that could bodyhop at will and has been doing so for thousands of years. And Nanami can copy Ninpo with ease. Not to mention knowing the same martial art which forces a soul out of a body that her brother knows.
So she can definitely copy an equivalent to magic, but IDK if Fate magic would be similar.
BRB, it seems I neglected to put Soul Manip on Nanami's profile.
1. Sigurd has no body, he's kind of a soul that doesn't need a body and just looks like he has a physical body and this is true for all servants. Even the blood he spills is only magical energy looking like blood. So no, no body to force his soul out of.
2. I am thinking it could be the case, but am not sure. On one side, verse equalization and all that jazz. On the other, Ninpo doesn't have and doesn't even use the equivalent to mana or magic circuits or anything remotely familiar. Even Kyotoryou, a martial art that doesn't seem to do anything to pull fantastic stuff off and isn't a Ninpo, can do something like pull out a soul. Personally, I could go either way.
3. For sure, plus Migeiri and the Ninpo Ashigaru means physical attacks are much less likely to work out... which thinking about it, wouldn't it mean Sigurd would be more predisposed to Runes or Bolverk as his opponent just doesn't seem affected by physical attacks?
2. It seems like if it's either a part of someone's physicality, or something that could theoretically be learned/taught, she can copy it. Servants have no real physicality, but Isn't rune magic something that can be taught?
2. It is something that can be taught, but like all Magecraft it's also a big question of do you have enough talent? Do you have talent in THIS area? Think of every human as a model of PC geared for something. The genius Tohsaka would be a high power, high efficiency computer that does a lot and does it all very well, while Shirou can barely run basic programs, if he can even run them, but his Paint is very good at tracing swords then smashing Control + C and + V.
3. Then it all depends if she could copy Runes or any magecraft. More input would be nice.
Runes can be taught, but Magic Circuits are necessary to perform the spells. Even if Verse Equalization allows for their "magic" systems to work similarly enough to affect each other, it doesn't mean that anything one side can perform is physically possible for the other. Even if Nanami can learn the theory behind the runes, she can't apply them since they're based on a similar but separate system. Like how one can theoretically understand exactly how a Stand works, doesn't mean that said abilities can be replicated without actually possessing the same Stand.
Which then brings up the same question, because Ninpo can be taught, but only generationally.
So it's like One for All where it gets passed down through a clan's family tree, growing stronger and more useful with each generation. Which sounds similar to Fate magecraft.
And Nanami can copy any Ninpo and maximize their abilities on the spot, even if her body is cursed by destiny itself to be anatomically incapable of doing so, completely skipping any training and generational leveling. This is literally impossible within the rules of the Katanagatari series, and she is called "an existence that should not exist" because of how big of a middle finger she is to her own series' worldbuilding and power system.
"Anatomically incapable" are the key words here. "Anatomy" implies physical limits, but Magic Circuits are spiritual. They're determined by the soul. Only IF Nanami can change the very foundation of her soul to gain Magic Circuits or something similar, then I'm convinced she can learn runes. Regardless, even if she could, it wouldn't change much. Bolverk Gram still destroys her.
Well, not really similar beyond superficially. It only happens in mage families because the Crest is made bigger by the head then passed down, normally they find some way to better the genes of the next generation and they usually just get better because genetics kinda play a big part in Magecraft (which is why many families just decay without a damn reason and anomalies without lineage but fuck powerful circuits are born, like mutations in the genome).
It gets better because of age, which matters in nasuverse, and because genetic anomalies aside, the family does tries their best to strenghten their progeny and better their craft as time passes.
I actually think Sigurd doesn't have much to damage her physically. Ashigaru plus her God Eyes means it's unlikely he catches her off guard, but he's likely to notice the odd way her body waves and flows and etc. So he'd try to freeze her with runes, if that's even possible, or directly attack with them. That's how I see it.
Would Ryuuryoku Kakou work on Sigurd? It's a shockwave that bypasses armor and skin to strike the innards directly, but as far as I can recall Servants have no real organs, just a "core". Would hitting that core directly be a win condition?
If so, Nanami might be able to win this, via dura negation, speed amping, and being able to break Gram with Daffodil.
I am actually not sure about this. Never has there been any case of something like this since the Servant is just energy imitating a human and I am not quite sure how it'd interact. What I do know is that the core is never interacted with directly no matter the type of ability, as far as I remember that is, it's only affected through the destruction of the heart or head as they are directly connected to it. I would say it doesn't, but she can go past his armor.
That said, those parts of the body shouldn't be any weaker than the rest of it. Kuzuki aimed one of his fist attacks to Archer's head in the UBW route after losing his Caster enhancement because she died, and he didn't even move it a millimiter where before he could hurt even Saber. And this is an Archer that is low on energy, yet he reacts as if wind blew on him.
Still I am super uncertain about this and would prefer some comments from others.
Basically, due to HG limits. It can't summon genuine heroes so it opt for creating fake copies of them. In addition they cannot interact with the world without having a "vessel" (physical body) so that they can freely exist in the world. This ultimately doesn't line up with previous post about servants being walking souls
Was there a retcon? Or am i just too impatient and it is expanded upon more during the routes? (Whichever it is)
Inferior copies is what Servants are, that's the whole point of the classes. They are vessels that don't summon the full might or abilities of the Servant but make it actually possible to summon them. As for the physical bodies, Servants are brought to the world by the 3rd Magic, or materialization of the soul so it doesn't need a physical vessel (flesh and blood body). But this application is imperfect and incomplete. A Master is not merely a mana provider, is an Archor so the Servant doesn't end up deleted by the World as it knows they are dead and shouldn't be. Because of it Servants have a core and an exterior that mimicks an human body. Hits to the head and heart are fatal not because of any organs, but because they are directly connected to the core and a direct hit strong enough pretty much destroys it, but even the blood Servants shed is actually magical energy and not actual blood.
Assuming Sigurd is just as skilled as Siegfried (I don't believe so but I am probably alone in that), Karna wins. The only reason 'fried lived that long was because AoF nerfed dozens of killshots into scratches. Sigurd dies really fast if he doesn't spam runes from the start and still dies even if he does, just takes a bit longer.
Also, time for Kratos vs Sigurd which is pretty much spite at this point since its like Achilles but worse.