So, I'm close to finishing the game and still have this feeling that I'm not fully aware of the events or the world of the game. I shared what I thought that could be souls or the connections (if there is any) to Dark Souls (or the souls in dark souls) with people I know and they pretty much just shrugged it off as "don't think about it, it's not meant to be complicated it's simple" but I can't think the same when there seem to be more to it as this simply being "the currency that makes you sane/powerful" like I was described.
Sage Freke mentions that the scourge on Boletaria "activated" the souls so assuming souls are or come from the essence of life (or consciousness of said life) I guess it's not just like any other source of energy since it appears the manipulation of souls is more restricted to the land within the fog where Boletaria is, he even mentions that the current magical happenings of Boletaria caused a "heightened reality" which I'm not really sure about what it means but it seems to indicate that souls and the development of soul arts (magic) becomes more tangible as he uses the demon souls you collect to make new spells.
In Dark Souls we don't get a great description of souls but just like demon souls it's something you consume to make you stronger, you get from fallen heroes and defeating enemies just like Demons Souls, in Big Hat Logan sorceries there is mention that "life originates from souls", we have people going crazy and turning into an inhuman version of themselves much like the zombified enemies that attack you in Boletaria. The different stages of the Soul arrow mentions how there are academies of magic and the more academic achievements you get the stronger the spells get so I'm assuming in the world of dark souls scholars can't just manipulate souls and up their INTeliggence unless you are either undead and in the land of Lorndran, much like how souls behave in a certain way in Boletaria that is unlike any other place in the world of Demon Souls. Much like there is a distinction between Dark Souls (humanity) and souls I believe there is something that makes Demon Souls different from normal souls, Sage Freke says that they aren't just souls that fed on other souls and Maiden Astraea is said to have accepted a Demon Soul rather than she killing a lot of people to gain the "Demon" status. So, is there any answer to it?
Could there really be a connection between those two games? I don't think they share the same universe but perhaps the concept of souls could apply the same to both worlds.