The plot convenience is strong in this story.
A normal girl can just cut through flesh with ease?
No magical buffs or video game status boost?
And some other random girl just so happens to be a sharp shooter that is instantly an ace at shooting even when it's her first few times using a gun?
Even professionals would not try shooting where she did, it's so risky since if she missed that tentacle (which is just a censorship for a penis let's be real) she'd have his Saya with those bullets.
Most people would off to shoot it's Gian body, but this girl just does the riskiest shot and somehow hits the mark not once but multiple times on that tentacle that was about to enter Saya?!
Absolute bullshit!
Sure it's fiction, and it doesn't have to be realistic, we literally have zombies.
But if you're basing them off as just normal highschool girls, then at least have some level of realism!
Even just a few, make her not take risky shots out of fear of missing, make her shake her hands since its her first time, have Saya actually hit by a few miss shots or even just grazed!
Writing fiction is not about being so unrealistic it's basically not real, it's about balancing fiction in a level of realism that isn't too devoid of realism!
Her being so good at aiming for a first timer is so outlandish when she's never even held a gun in her life!