Honestly, I kinda pity the dude, because unlike 99% of other heroes, HE'S NOT EVEN AN ASSHOLE. Like, the dude is legit a nice dude, he's someone I'd at least not hate the idea of hanging out with! He's got good morals and all that! He's just dense and not even in the typical harem protag way...
I legit wouldn't be surprised if the author is INTENTIONALLY avoiding machine pistols/SMGs because they're so universally useful for most situations. It's not very interesting to write/draw/plan fights if the SAME answer almost every time is 'take out an SMG and go nuts'. So they go more for...
Frankly, I really do feel more for the girl than the MC. She doesn't seem like an asshole, she's desperate to help her friend, and then this random dude basically shits all over years of life-risking effort with casual and contemptuous ease. Fuck, I'd be pissed off, too, and have no real way BUT...