If I am not mistaken, the current world record is at 42 minutes!

The craziest speed run is The Legend of Zelda: OoT. Fully exploiting every bug in the game, one guy finished it in 18 minutes. Some people take speed runs very (almost competitively) serious.

I found Dark Souls at 23 minutes far crazier than OoT's speedrun

When you think about it, the levels in Demon's Souls are quite small, and there aren't many of them, so if you're good at not dying then the game can be done with quite quickly.

I did my The Order hard playthrough (first play through) without using Blacksight at all (I forgot it was a thing, so it wasn't a deliberate decision to make the game more challenging). With Blacksight I think even on hard the game would be a bit too easy. I only had a few fire fights that caused me to die a number of times, anf if I'd rememberd about Blacksight I doubt they would have presented a challenge at all. Probably extended my play time by about 2 hours over all. Personally I think bullet time is a cheap trick and I prefer games without it. It's only real purpose is when you have an overwhelming number of enemies and it lets you clear the field more easily. Good game design is having you play gun battles at normal speed and never have waves of enemies that are impossible to defeat because of sheer force of numbers.  I've proven that The Order's version of bullet time is unnecessary to play the game on the hardest difficulty, so they should never have used that cheap trick in the game. I kept wondering why snipers were so insanely accurate and instant with their shooitng, but of course after the game was over I realised I was supposed to use Blacksight to take them out. I imagine for a speed run, and for getting through with no deaths Blacksight is needed for most people. I would certainly need it and even then I would no doubt die a few times.