Thanks, @Player. I didn’t read the entire manga, but the tactics displayed in the early pages would be counter-productive against Theurgy (let me know a specific pageref if you have something different in mind). Even at rifle range, any Theurge who could see the rifles could mince the whole squad with a couple of blood phials, using solely the gunpowder in the adversary’s own guns.
In the first half of Game 2, the MC will get tutoring in more of the detail of how Theurgy works – including some new skills that will make @HomicidialFrog happy. For now, I’ll just say that there’s a sense in which black powder really wants to explode, more than any other substance in the gameworld. That volatility is conspicuous to a Theurge who’s looking for it, so it’s not easy for someone carrying powder to remain concealed. And it’s very easy for Theurges to accelerate that potential, creating a much bigger and more destructive explosion than you’d get by simply striking a spark to the powder.
So bringing black powder to any fight involving Theurges would be foolish – a bit like trying to use liquid nitroglycerin in combat. It’s much more likely to kill you than your enemies.
Now, you’re right that if the rifle had been invented in the gameworld, its long range and accuracy would still make it an effective assassin’s weapon. Under circumstances where you were taking on up to four Theurges from cover… it would be a gamble, but if you had a good rifle, you’d have decent odds of taking them all out before one of them sniffed out where your gun was and blew you up.
But the evolution of firearms on Earth took centuries, starting (in the West) with adapting bell-casting tech to make cannons. I’m suggesting that in the gameworld, that process of evolution stalled before it had a chance to get started. Just as cannon-making was properly taking off, Karagond Theurgy was developed, and the armies that had started to use crude artillery were literally “hoist by their own petard.” The lesson of those early conquests was that black powder weapons are worse than useless.
So rifles don’t exist, because even if a visionary imagined the idea, s/he would have no practical tech base from which to work. Whatever early attempts there were at making hand-held cannons, they never got anywhere close to the stage where someone would think to experiment with something like barrel rifling to make it more accurate over long distances. And at short distances, or long distances with poor accuracy, firearms vs. Theurges is suicide.