Spoiler free review!
It's Not Meguro-san's First Time tells a story of a 2nd year high-school student Meguro, a girl with a reputation for dating and sleeping with any guy that asks her out and Koga, a 3rd year, who oblivious to the rumors surrounding Meguro asks her to be his girlfriend to which she agrees without any second thoughts.

Koga quickly learns that Meguro is not a virgin and has a lot of experience, as she makes no attempt to hide it.
To Meguro’s surprise, Koga has no interest in sleeping with her and dumping her right after.
He is genuinely interested in learning about Meguro and having a real relationship with her.

Koga, trying to live up to her ex-boyfriends, works very hard and does his best to satisfy her on their dates.
Meguro, on the other hand is often taken aback by his gentlemanly and innocent behavior, especially when she’s used to the guys being open about wanting only her body.
The contrast between both experienced Meguro and completely clueless Koga sets up an interesting plot, which makes for a very strong and mature start to the story.

For the reasons above I absolutely adored this manga after the first 10-15 chapters.
Unfortunately, the story gets less and less interesting every chapter with small ups somewhere along the way.
Past the middle point, I was forcing myself to finish it, as I was still curious about how it ends and I regret that I didn’t drop it sooner.

Reading this manga, you quickly realize that each chapter has the same uninteresting structure, usually ending with an awkward monologue of either Meguro or Koga about their love.

This happens in almost every chapter, while at first it’s interesting, later it gets obnoxious and insufferable.
Both main leads give monologues as if they have all the knowledge about life and real love, while at the same time they’re high school students who don’t really have much actual experience with either of those.
It feels like the author is using the characters as preachers, who exist just to put the author's pretentious speeches out there.

Not to mention, the characters don’t really talk in a natural way like average high school students, which feels very jarring and takes me out of the story every single time.
Although, that may be an issue with the fan translation, as I don’t speak Japanese, I can’t verify it with the original version.
Nonetheless, be aware that if you’re going to read this manga in English, some of the dialogues sound kind of unnatural, which may affect your enjoyment.

The drama that rarely arises usually starts and ends in the same chapter or at most the one after that.
With each chapter having around 15 pages, they don’t leave much impact on the reader and you quickly forget that anything even happened.

The manga also features few side characters and their relationships but neither them or their relationships are interesting in any way whatsoever and not much time is spent on them for the reader to actually care.
They suffer from the similar problem of the main pairing, where any drama is very brief or feel forced.

I have to mention that the two main characters do grow together and change for the better throughout the manga. It's nice to read how the main couple supports each other and how they deal with their unusual relationship.
Some of their moments are very sweet and heartwarming and this is definitely something this manga does well in some parts.

Although the review is spoiler free, I cannot review this manga without mentioning this aspect. You can skip the following two paragraphs if you don’t want to see any spoilers.

As for the art itself it’s not something I can really complain or really talk much about.
It’s not the greatest art ever, but it’s pretty decent. The backgrounds don’t have much detail to them but there are plenty of pretty panels at some important moments.
The characters are distinct and easily recognizable and the main heroine, Meguro Saki, is really cute too.

All in all, I don't recommend reading this manga. The initial premise may be interesting, but the author's inability to create an engaging story without forced drama makes for a very weak series.
It could be a really good manga, but unfortunately it wasn't for all the reasons I've mentioned, which makes it really frustrating and disappointing.