I've just skimmed through the comments because it's honestly hard to even look at them. Did people actually read the manga, or just the title, synopsis, and maybe a few first chapters? Or maybe reading comprehension in the general public is just that bad. I have no idea.
I honestly don't even know where to start.
Meguro is not a slut. Not even close. She is way closer to a maiden archetype than probably anything else. Meguro did literary nothing wrong. Or more precisely, she didn't do anything in her relationships. She possessed no agency, hence she didn't make any decisions. Everything that happened to her is a reflection of what her partners were looking for in one. At the same time, she is loyal and committed to her current relationship basically from day 1. She doesn't care about appearances - even less so than Koga - and wants to make her partner happy, to the point of being completely and unhealthy selfless. How is that a "slut"?
Going from that, I have no idea how anyone could read the story as glorifying or justifying promiscuity when due to what I've just mentioned it's exactly the opposite. IMHO the story criticizes the disposable approach to relationships in modern culture. Meguro only had so many boyfriends, because all of them were either using her for cheap gratification or weren't committed enough to even bother to know her, someone they were allegedly in love with. Koga didn't do anything special in this story. He just started a normal, committed relationship with another person. Well, I suppose accepting that kind of baggage with no qualm would be more realistic for someone who is 25+ and actually knows and accepts how the real world works, but it's not too much of a stretch for 18 y/o to be able to do it too.
For some reason, many people also keep going back to the fact that "she is not a virgin" when it's barely a premise of the story, not the theme. Hell, it was mentioned like 3 times and maybe once in a way meaningful to the story - when Koga spoke with her sister. The most prominent theme is the acceptance of different people. Because your normal is not necessarily someone else's normal. Because there is no one definition of love or friendship or any other relation. Because you can't change the past so dwelling over it is meaningless and all you can do is your own thing, now, and as long as no one is getting hurt, leave others to do it their own way.
And yes, Meguro is kinda weird. Because she was damaged at a very unfortunate age. Funny thing is, that I don't really think that Sensei's approach to relationships is inherently wrong (age/experience difference aside - I don't think he was malicious in what he did, but he should have known better). He just pushed it on someone with absolutely incompatible ideals, which in turn caused damage by creating a disconnect between what Meguro actually wants - a committed relationship with a strong connection between partners, where you work together, support each other and overcome all obstacles - and what she was "taught" - that relationships come and go and there is no point on dwelling on them for too long, accept what comes, enjoy the moment and don't think about the future. By the time we reach the beginning of the story, she is at a point where the gap between what she seeks and what she found by accepting Sensei's advice is so wide, that she pretty much gave up and just going with the flow, waiting to be rescued.
Some issues with pacing aside, it's a pretty good story. Going by the rating of other manga on the site, it would probably be 8.3ish if not for "arg not a virgin, burn the slut" kiddos.
No idea why the Drama tag is first on the list since Drama is pretty much non-existent in it.