@lonelypotatoonabench
If you completely ignore the fact that progress between the two main characters is slow, this is definitely an enjoyable read. It's funny enough, and you begin to notice that Manabu is actually really sweet and thoughtful as you continue to read the series. There are some genuinely good moments. The side characters are fun, too. If you're into ecchi, the fan-service is definitely something to look forward to.
I don't think it's such a bad thing that the progress is slow, since at the core, this is a slice-of-life in the truest sense. It's everyday life, so you get to see a lot of days where nothing of note really happens, except the shenanigans of the main characters. I guess in that regard, you could say the progression of their relationship is really organic and natural, even if it is slow. Each year in their high school life is roughly 100-ish chapters, so that should give you an idea of how slowly time progresses in the manga. If you like that kind of slow-burn, then I think that this is worth checking out.
Anyway, I think the main problem isn't the way that the manga is structured, since this
is the way that the author intended to write it and it's quite clear that he's still enjoying writing it, after all. I think the main problem is that some readers expect rapid development in the relationship when nothing in the manga tells its readers that the relationship will be developing quickly. It's
slow-burn, so if they don't like that, they can just look away and look for a shorter series, since the author probably wasn't writing this with them as their target audience. The frustration from reading a slow-burn work its course is a natural part of the slow-burn experience and it's part of what makes slow-burn enjoyable, at least to me. I like feeling frustrated because the payoff when it finally comes is that much more satisfying when it's done right. I just think it's kind of stupid to expect things to suddenly pick up in pace after the setup of the manga has told its readers to strap in for a
long ride, and to cast that natural feeling of frustration as a sign that the manga is bad and throw that opinion out willy-nilly.
The manga is not bad by any means. It's not a masterpiece, either, so if you want to turn your brain off, this is a good read. Sorry for the borderline-rant and the wall of text, but yeah.
TLDR: Turn off your brain, don't think too hard about how long it will take the main characters to make their relationship official, and this is an enjoyable read. It's good ecchi, too.