A/ such relatively homogenous steel would still, at the time, be folded and have grain. B/ equally in Europe as in Japan. C/in the one closeup I see several spots of what I'm pretty sure are folds/lamination.
I disagree that bigger pictures, overall pictures are liable to tell us much more though I'd enjoy them; closeups of the blade would probably be the most useful, and we have them. More would not likely tell us more, except that it might be useful to see the tip of the blade (though if it's "correct" that tells us little, and if it's "incorrect" there is much more variation in old Japanese swords than people often seem to realized, so that tells us little, too.). I think the guard/seppa(and there are similar features on many European swords; sheath lids, oval discs, and leather and felt washers of the seppa shape)/habiki was cast in one piece. I'm not certain, but that's my thinking. Look inside the piercings; look where each flows into the other; I see no join lines, though certainly such can be cleverly hidden. I do not think the silver ring around the edge is a layer; I think it's a ring soldered into a groove. This is guesswork based on what I can see; it could be wrong; those brass coloured flower centers could be rivets, even. (photos.....
) I still see nothing to argue for an Asian origin for this heavily Asian-influenced object. The Ottoman connection seems interesting, but the handle construction seems European? One thing worth noting is that the blade seems to have a shinogi zukuri cross-section; sabre-bevelled with a (somewhat rounded and indestinct, but present) ridge down the middle(ish) of its width.