Coming back to re-read this after the 3rd or 4th time, I can understand some criticisms noted by previous comments, but to those I would like to point out that the author (and artist) only did this in 28 chapters. It wasn't meant to be drawn out, and with more than a "good enough" ending to it. Sure, there will always be questions lingering, and characters may not be as flushed out as other manga of this type, but they also had/have far more chapters just to address those issues, many of them failing to do so or do it well.
This was meant to be a short read, hit the key points and flush out notable characters enough to satisfy the reader, and then end well. The main protagonist doesn't always need to develop into this perfect person over the entire course of the work, but they do need to show enough to satisfy most readers, which I think they did. The antagonist doesn't always have to have a tragic background to force the readers to like them or feel less bad for them because they want us readers to have our dilemma in justifying the antagonist's actions. It's weird how people don't see that having a straight-up, irredeemable villain in a good story nowadays is actually in the minority, but it once was everywhere in movies.
I know this is going to sound weird, but this manga kind of reminds me of the golden-age Disney movies. People who watched it remember their villains, even though there was nothing good about them in most cases. They didn't need to be redeemed, but they needed to have a satisfying end. The heroes didn't need to always have a strong build-up, but they needed to give them enough development to enjoy their short journey, and satisfy the viewer with their victory.
Is this a Disney classic? No, but I think it's a series that should be used to compare the story of other mangas to this one, especially in the same genre. It's not demanding you to read 52-100+ chapters for your time (or to catch up) with about the same payoff. It's a book you would read over a weekend, and it thanks you for reading it. I recommend it to those just getting into manga for the story— instead of for fan-service reasons— because it's not the tip of the iceberg, but the start up a grassy hill before your real trip up Kilimanjaro in a spiral, with all of its weird weaves through the mountain to a peak you may never reach. You'll still look back to that soft, simple, grassy hill that you started your journey on.
(Sorry for the weird similes, metaphors, and/or comparisons. I get weird if I ramble too long, but please give this story a try.)