Demon's Souls was basically remixing what Ninja Gaiden perfected.
The Souls games are far more like Severance Blade of Darkness than Ninja Gaiden and Severance was released way back in 2001 so if anything it is "remixing" what Severance did.
I have never played Severance, but looking at gameplay videos I can see why you draw the comparison. However, my point was narrowly focused the combat itself. While there are similarities between the two, it's not clear to me whether the combat is in fact lock-on or not and it appears that there is animation canceling, the omission of which is IMO one of the most important features of *souls combat.
Either way though, as that game appears to have sold poorly and to be a PC release with no Japanese release, the chances that it influenced Demons' Souls is very low (although still possible). By contrast, the Ninja Gaiden games were very successful and had the Sigma edition and/or Ninja Gaiden 2 released shortly before and during the development of Demons' Souls. Any console action game developer, let alone one thinking of using lock-on combat, would not only have been highly likely to be thinking of how their gameplay would stand in comparison, they would have been negligent if they failed to do so.
But Souls combat shares few central characteristics with Ninja Gaiden. You seem to focus entirely on lock-on but Ninja Gaiden didn't have stamina and it didn't have particularly weighty weapons, both of which are less ubiquitous than lock-on but still just as, if not more, defining aspects of Souls combat. Jumping and special key combination moves are also central in Ninja Gaiden and Souls has neither.
Nioh on the other is very similar to Souls games right down to the lower left corner equipment switch UI element. It is obvious that is heavily inspired by Souls games to say the least.
If looking for popular console games released in Japan which Souls games could have drawn inspiration from then Monster Hunter seems a likelier suspect than NG what with its stamina system and weapons that have wildly varying weight. On the other hand it doesn't have your lock-on so it does not count
Ah yes, the eyeroll emoji, quite an effective refutation - now I am thoroughly convinced
. Monster Hunter could certainly have been an influence, games can have more than one! (although its combat looks very imprecise and "floaty" [for lack of a better term]).
You mock my focus on lock-on, but the presence and degree of lock-on (i.e., camera lock vs just targeting lock, whether its automatic or under player control, etc.) used in the game has a dramatic effect on gameplay in the way it affects how blocking and dodging function, the relative importance of positioning and timing, the importance of situational awareness and, often, whether combat with groups consists of a wild melee or a series of overlapping/alternating duels (which in turn can affect encounter design).
Additionally, while I have focused on lock-on, I have mentioned the importance of animation canceling to the souls experience, especially when combined with relatively slow weapon speeds. The forced vulnerability of that weapon animation is as important as the stamina limitation for forcing you to make good decisions. (also animation canceling, camera lock (vs aim lock) and the defense oriented rhythm is also something separates both Ninja Gaiden and the souls series from more chaotic brawl oriented combat of games like DMC, God of War etc).
What this adds up to is a comparable combat loop of defending to await a vulnerability, then attacking until the window closes and returning to a default defensive posture, all of this while maintaining wariness about what non-targeted enemies are poised to do in your blindside. Of course my opinion is also based on various kinesthetic parallels I feel in the gameplay that are difficult to describe and highly subjective anyway, so I've avoided mentioning them. But if they are not shared, I can understand why what I'm saying sounds absurd.
Certainly there are very significant differences, with the jumping and acrobatic nature of Ninja Gaiden that you identify being possibly the most dramatic one. This coupled with the overall speed of combat leads the games to feel very different despite overlapping mechanics.
The combo issue is significant, but not black and white: you can play through Ninja Gaiden without mastering combos as long as you have a few combos you can rely on as long as you have mastered the block/counterattack loop. Similarly, while you do not need to do so, if you want to play optimally with some of the lighter weapons in Souls games you do need to master their (simpler) combos. Weapon weight differences are, in my a opinion, partially a distinct feature of souls, partially a result of Ninja Gaiden having a much higher speed overall, as dabilahro and the hammer, for example are relatively slow and heavy, but still much faster than souls game heavy weapons.
Also, I did not argue that Nioh was not heavily inspired by the Souls games; it clearly is. Their success has rendered them the elephant in the room for anyone designing an action game of the sort, just as Ninja Gaiden was prominent when Demons' Souls was being designed. Again, my argument is simply that combat in souls and combat in Ninja Gaiden share DNA, not that the Souls games have no other influences or that Nioh is not influenced by the Souls games.
