If you look up the manga on "en.accessup.org," a Japanese rankings/ratings site, you'll find that this manga has horrible ratings. A lot of the hate comes from the fact that the author bragged on his twitter that his series is better than many of those on Jump. But I'd like to try to comment on this manga with an unbiased opinion taking into of the author's history.
Pros:
Especially for a newbie mangaka, his art received a lot of praise, and he deserves it. Some of the scenes are pretty epic and the s are divided quite well. Kendo is a pretty difficult sport to draw. If you compare it to other popular Kendo manga in Japan, like Bamboo Blade, the matches in this one is much less sloppy and readable. You can enjoy the sparring because the author allows you to keep track of the movements of the characters. The characters are easily distinguishable by personality, face, and name, something that troubles a lot of inexperienced manga artists.
The theme of the manga is pretty exciting, you have the main character who's intelligent and has powerful kinetic vision, but falls short in of strength. The ghost Sayuri then haunts him (and hangs around as a cute character when they're not alone), wishing to down her style of kendo that failed to leave its mark in history. Similar to a new Hikaru no Go scenario. The appeal of this manga as a sports manga comes from the fact that there are not that many kendo manga despite its popularity in Japan. People who are new to kendo find themselves attracted to this manga the same way Eyeshield21 appealed to readers of WSJ in Japan.
Also, although the manga is a little bit too predictable with shonen cliches here and there as said by the other comments below, the pacing is pretty good. There haven't been any really disappointing chapters in which the quality suddenly drops. The story's pacing is neither too fast nor too slow.
Going through the manga, I think one can thoroughly enjoy it depending on the person. So I would say it's worth a look for those who have nothing to do.
Cons:
One thing that's heavily criticized about this manga is that the characters are too shallow. One thing that really bothered me from the start was the whole thing with Kurogane starting kendo because the desire to "stand out and be a hero." It is irable for him to have the determination to become strong and meet the proper friends and rivals that help him pursue that path, but I think he could've started to exercising and gain stamina + muscle strength at any given time, rather than start off weak and try a bunch of sports, knowing that he'll probably fail. I always found it corny right from the start that his reason for starting kendo stems from such an idealization; is he an elementary school student? And then we have our enemy kendo participants who are sadistic, arrogant, and disrespect what kendo is about, something that would be harshly castigated in real Japan.
2nd thing that's a huge issue with this manga is that it does not represent real kendo. Some parts of the manga explain kendo concepts quite well (like the captain's Joudan and Shidou's one handed kendo techniques) but much of it is false. I am a kendoka myself so I'll give you some examples drawn from my experience.
First off, how Kurogane's team switched positions so that Kurogane becomes the sacrifice general in the practice match. That would never happen in real life for something that is only a practice match. In fact, it would be considered cowardly. Practice matches are used to gauge each team member's abilities so each position is given with respect to each individual's talent.
In one of the 1st year matches in which Shidou defeats his opponent, he knocks his opponent's shinai away. In fact, he breaks in half. That would never happen in real life and disarming your opponent is not even part of kendo.
Some of the "techniques" are just ridiculous and have no place or purpose in real Kendo. Such as knocking out your opponent so he falls down with a spin technique.
The "Sakura One Strike Style" couldn't possibly work in real life, and it's even more impractical for someone who's a complete amateur to use it. Kurogane's Samidare, which is basically telling your opponent "look here, I'm going with a strike that's definitely going for a tsuki, the hardest area to hit in kendo." Not to mention that tsuki is only learned after achieving 1st-Dan. It's a technique that can hurt people if not executed correctly but Kurogane is using it all the time as if there is no problem."
Oogami's method of running around and executing continuous attacks is more like old-style Kumdo then Kendo. Kendo is about reading your opponent's movements, looking for an opening, and making the perfect one strike. Kendo exhausts a lot of stamina; that method would just burn you out before overtime.
There was also one instance in which one of the participants used a street fighting stance to mess up his opponent's ability to read his rhythm; that's just insulting sword arts. You can't just make any BS stance and use it to catch your opponent off guard.
I don't mind the supernatural twist that Kurogane's phenomenal eyesight brings to the story, but I dislike how the author made eyesight a standard that measures a kendoka's ability. Increased kinetic vision does not exist in real life and as long as you wear sport-glasses or s to actually see for those with poor eyesight, it's completely fine in kendo.
In one of the arcs, a team specializing in Nito Ryu, two sword style, showed up in the competition. However Nito Ryu is prohibited in elementary, middle, and high school competitions in Japan. The ban on using it was only lifted from college competitions and up. It's also highly recommended not to use such a style at such an early stage of a kendoka's development. Also, they make it look like using Nito Ryu is a big advantage but it isn't really. Using 2 swords rather than one is very difficult to be proficient and someone using only one sword but has more skill can easily overwhelm the opponent.
But to make it worse, the team uses two shinai "both with the same size." There is no existing style in history that utilizes two swords of the same length, because it's just not practical. Nito Ryu is a technique developed from swordsman, Miyamoto Musashi. But that technique involves one Katana (long curved sword) in one hand and one Wakizashi (short curved sword) in another. So Nito Ryu in Kendo is always with one regular sized shinai and one really short shinai.
Not to mention, the stance of the guy with the two shinai was all wrong.
It's also important to point out the plot holes in the early parts of the manga. Kurogane couldn't swing even a regular sized shinai in the first chapter without the help of Sayuri, but he's weaving it around [while wearing full armor] a few days later without any practice and training in between. It also doesn't make sense that he even knew how to wield a shinai properly the first time using it, which takes days of training to learn it.
In kendo, if you don't hit your opponent with the shinai hard enough, it doesn't count. For those who read Bamboo Blade, you know this when Tama-chan's one handed men strike didn't count because the strike was too light. If Kurogane is that weak, he probably wouldn't be able to use strikes to hit hard enough to count at all.
One more thing I'd like to mention is.....who on earth has the time and energy to speak to each other during a kendo match. Concentrating on anything other than your opponent is considered an erroneous move in kendo, but the characters are either arguing or talking casually to each other while fighting....when they're supposed to be screaming in spirit. In Kendo you shout the area you hit. So you shout "MEN!" if you aim for the head, "DO!" if you aim for the side, "KOTE!" if you aim for the wrist and "TSUKI!" if you aim with a thrust for the throat. If you make a hit without the shout, it's not supposed to count, but they don't do it like that in Kurogane.
It kind of does apply to any sport that you focus your attention on the match but in manga, it can't be helped that the people are talking in the midst of everything. But the author goes too far in that he makes the characters have casual conversations.
