Though Mega seems to act iffy for me. Is it possible to upload it to another sharing site? I understand if you can't, still thank you again.
Truth be told, I have yet to upload anything myself, and I'm not sure how long it would take to familiarize myself with said process. - (When I find the time.) So until then I'm gonna name drop
FirstForm here, as he already helped someone else in a similar/the same situation as you. (The link he gave that person is sadly expired.)
Here is also another MEGA-Link in case you might have a bit more luck this time.
https://f95zone.to/threads/shrift-v8-06-devils-office.67613/post-7889728
I'm pretty sure when you first get to a safe room and the sp machine is explained to you, it's mentioned offhand that some soldiers brag about how many demons they killed to get stronger. Killing demons itself doesn't make you insane and he is a captain known for his combat prowess and tactical ability so I assume he's killed at least a few. Kazuya's insanity probably stems from being the target of intervention.
At first I thought that a "normal" humans' SP was supposed to be more of an innate potential each individual would have access to through the capsules. - Meaning, same as in our reality, everyone is different, - some might have a higher SP value/potential than others. - Hence the brag. The exceptions being both Kazuya and Yuuma, who can actually get stronger through killing and/or bonding with demons.
But even if we say that "normal" soldiers can, in fact, get stronger by killing demons/sending them back to the demon realm/being exposed to them for certain amounts of time, their increase in power can't be all that huge. - They also don't seem to have access to the "Magic" side of capsule-upgrades, by the way. (Correct me if I'm wrong, though.) We only ever see them fight with their guns... and being killed off shortly after, without them ever resorting to anything else.
Compare that to Kazuya, who, after giving the others a head start of
5 years, and no matter which route you are playing on, is more than a match for Empuse by the time he gets to her.
Now, back to Yuuma.
"Killing" demons shouldn't make you go insane by itself. Probably true.
Yuuma not being a target of intervention is definitely true.
Here's the kicker though: After you leave the "Barghest area" behind you, (GENOCIDE-Timeline) Yuuma will warn and implore you to not kill any more demons out of idle curiosity, with his explanation being that he himself did just that, only to notice his own sanity slipping away. - The same thing that was happening with Kazuya in that very moment.
So... what could be the cause? Well, there is in fact one thing both Kazuya and Yuuma
do have in common.
And we can go even further down this rabbit-hole. Our dear Lord Cushion explains to Kazuya that he can't really pass on, because his very soul/being is infused with magic, - which shouldn't be. You can probably guess where I am going with this.
By that logic, Yuuma could, in theory, have also had access to Hell's Gate and My Rooms until he was defeated by Daji.
...Hence my rather silly articulated question in my last post.
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Admittingly, I am aware that this story is about Kazuya, not Yuuma, but still, I like my mental gymnastics, and not everything has to be directly tied to the Protagonist to add to a story in a good way.