The long story short is that, despite having characters anticipate a sexual assault (and showing a panel of a woman on the ground with torn clothing), the writing is at a 3rd grade (elementary/primary school) level.
The plot so far, as little of it as we have gotten, is consistent as of chapter 12.
But the antagonists are cartoonishly obvious and oblivious, characters talk in front of other characters but aren't heard in order to set up a later reveal, the author's voice cheering on the main characters comes through very obviously when other characters sometimes talk in inhuman ways to make a point about them, and the dialogue generally feels like it's far too simple to believe teenagers speak that way, let alone adults.
And honestly, I wish the main characters were already in a relationship. They spent years in another world together, and they think the world of each other, why wouldn't they have gotten married in the other world? That would have been so refreshing: a couple who go have dungeon adventures together in an ever-thickening plot without the stupid "will they, won't they" noise that, in a story written to such a low standard, will only be done poorly since you need subtly and nuance to pull that off and this story just doesn't have those things.
I like the concept, I like the art, I like the main characters... but this is something that just isn't written to a standard to make decent use of what it has going for it.
For anyone who thinks I'm being harsh:
Did you know the NIV translation of the Holy Bible is written to an 8th grade standard (which is why it's easier to read than the ESV, which is written to a 12th grade standard)? That's how far writing has fallen in the past decade.
Still don't believe me? When I was in the second grade, I was reading the Magic Treehouse series and it wasn't as poorly written as most of today's fan service filled manga and manhwa.
Quite frankly, reading this story hurt. It hurt because there were constant glimpses of a better, more mature story but I still couldn't get away from feeling like I was watching a show meant for young children. It hurt because it reminded me of how much I've been putting up with bad writing and for how long.