Aka: probably the most self-indulgent essay I will ever write. Otherwise known as the way that the events of the demonverse have summarily knocked out every mechanism Konatsu uses to support his ego and fucked with his issues in very delicious ways.
As the title implies, this will be broken down into the four primary mechanisms that Konatsu uses to prop himself up and make himself not feel like crap. If he can have all of these things, he generally feels pretty damn good about himself. If not, then, well . . .
Victory/Prestige
This is the most basic for Konatsu. If he can excel at something, if he is more talented than anyone else, if there is something that only he can accomplish, he feels good about himself. It's proof that all the time he spent growing up pushing himself to the limit to become the best swordsman in his class at the academy, all the time he spent studying his ass off and being a diligent and dutiful begleiter has paid off in something. He's ascended to a level that no one else is at, he's no longer the one who's snubbed and cast aside as second-rate. Being the best at something makes him feel good.
In the demonverse, Konatsu is pretty much the best at nothing. There are people who understand the world better than him, people who can sense demons better than him, even people who can do simple things like relate to everyone they encounter in the world better than he can. Essentially, for everything that Konatsu tries to do, there's someone who can do it better. He tries to overcome this issue in a really not healthy way of going out and trying to find things to do with himself that no one else can do. This is why, nine times out of ten, Konatsu is off on his own making a bad decision. He's hoping that one day one of those decisions will lead to him being victorious and being praised for it.
So far that hasn't worked out so great.
Utility
Somewhat related to the first point, one of the key elements in how Konatsu relates to pretty much ANYONE is in terms of utility. If he's useful, if he's contributed something to them, if he's helped or accomplish some task, then he's necessary and work keeping around. The second part of that is less a conscious decision and more something that's just ingrained in him with the really fucked up way that he was raised. But this point, essentially, is the basis of any friendship that Konatsu forms. For him to be comfortable in the friendship, he needs to feel like he's of use to the other person, whether in terms of offering emotional support, making them happy, etc. As such, once someone tells him that they're his friend, he'll immediately kick this insecurity into action, looking for a way to make himself useful.
Demonverse wise, Konatsu has kind of proven himself useless, very much pursuant to the first point here. What he tries, he generally fails at, and even when he doesn't fail, someone shows him up. As such, if he's given an opportunity, any opportunity, to do something that might prove useful: a suicidal volunteer mission, attempting an almost impossible escape plan, playing question games with demons he's going to go for it regardless of the risk. If he can prove himself useful in these regards, he's done something. Similarly, this is the reason why whenever people belittle him because of his previous actions, or look down at him and hold his previous mistakes against him, he sort of lashes out. He doesn't want to be seen as someone who's just dead weight and can't be left on his own if you want him to accomplish anything. He wants to be an actively contributing member of the group. But if the entire group seems to disbelieve that he can be even that, he'll, again, go out on his own in an attempt to prove them wrong.
Yet again, results are generally pretty disastrous.
Power
This one is a bit more tricky because Konatsu's relation to power isn't very cut and dry. Long story short, Konatsu is hypersensitive to the fact that he was born without power, and he would love more than anything to reverse this fact. However, he has a lot of pride and for that reason is incredibly unwilling to gain power at the cost of his own agency and autonomy. He wants to prove that he himself can be powerful, not that he can be powerful when being manipulated at the hands of some other higher powered being. This is why his sword skills are very important to him, and why he takes combat so seriously. He's essentially utterly outranked in his military unit and he's got to prove it (most to himself than to anyone else) that he deserves to stay there.
Demonverse wise: the sword. In all honesty, Konatsu was willing to take the sword's pact the moment it was offered in the very first game, but he wanted to know what he was getting into. When he agreed to go along with it in the second to last game, he only did so because he'd convinced himself that this was not an instance of him allowing himself to be used by the sword, but rather that he would be in a position of power using the sword's power to his own ends. Obviously this didn't work and obviously he got screwed over. Literally.
Sex
WHICH IS AN AWESOME TRANSITION TO THIS ISSUE. Okay so sex is like Konatsu's ultimate fallback tactic. Hilariously, he uses this in camp even though sex is forbidden. Basically, if everything else is failing, if Konatsu feels like a useless, powerless loser, he goes for intimacy. Aka: Raph. Since Raph is pretty much the only person (in camp) he's done this with and Raph (and Nii) have only ever praised him for how responsive he is in bed, Konatsu feels good about himself when he's making out with someone and letting them utterly top him! He's wanted! He's needed! All in all, it feels good. Because for him there's nothing like feeling that he's the only person someone is focusing on at the moment. Knowing that he can make them feel just as good as they're making him feel. It's a very fulfilling sort of mutually fucked up thing, really.
Until demonverse went and fucked this up too (literally, har har) Honestly, even though Konatsu was using sex as a means of restoring his own sense of self esteem, it's never really occurred to him that sex can be used for other ends. So when the sword made a pact with him, fucked him, then left him in a proverbial ditch to die, he felt violated, dirty, and pretty much sick to his stomach. It was essentially a direct whiplash from being wantedneededpower to being half dead in hospital room. And it's planted the idea into his head that people don't really only have sex with those they want or need. It's something like power, in that you can use people with it as a means to an end. Konatsu is really aware of how sex fulfills this purpose for himself, so as such he's hyperaware of just how much he's been duped. He's uncomfortable with the idea of intimacy now, because it's not just about him, it's about the other person as well. And not just in that "I am making you feel good" way. Even though, granted, it was with a demon, it's planted the idea in his head that sex can be used as a dupe, that everyone has their own motivations for it.
SO PRETTY MUCH. Right now Konatsu in the demonverse is royally screwed up! \o/ He's been defeated, not only by the demons they've faced but also by the people around him who've handed the situation much more capably than he has. He's useless, in that he provides nothing unique to the group, nothing that they can't just as easily rely on another group member for. He's weak, especially in the face of such massive power, and he knows that there's no way to attain anything even close to those powers without it taking advantage of him. Aand he's violated and detached from the one last resort that really would've given him some semblance of solace throughout it all.
tl;dr: boy's fucked up