Shamo's initial strength is Akio's talent for building atmosphere and use of symbolism that gradually starts to disappear, though the occasional flourish still graces the page until the conclusion. Once it establishes itself the series makes Ryo's story one of fear and domination. With family, in prison or in wider society his driving motivation is to feel that he has control over his life. He often expresses this through violence and abuse that demolishes any possibility illusion that he's a misunderstood young man in a bad situation. He is a violent, unrepentant criminal who endured a system that actively disincentivises even trying to reform. Importantly Ryo Narushima never asks anyone to sympathise with him. He's not interested in wealth, status or acceptance which makes him an anathema to his various rivals. Though this self-awareness never bleeds into tangible regret for the many violent crimes he commits over the 30 volume run. Ryo seeks to destroy Sugawara and rob him of everything is solely to ease his own mind.
The series' fault however is that by Volume 14 it has lost all direction. Spinning out into multiple bizarre storylines removed from anything that made Ryo's story engaging to that point. Most famously is the China arc. Initially starting strongly it takes this relatively ground presentation of martial arts and makes it focus on how to master Chi. Not in the sense that it focuses on Chinese martial arts and how their teachings are applied to combat sports. It’s about learn how to blast someone across the room with your spirit energy. And you can tell the creative team weren’t happy with this because they never revisit the topic once the arc concludes.
This might be explained by just not knowing what the series should be once the initial arc resolved. Maybe it is the natural impulse for a creative team who are interested in martial arts to experiment with different types of forms and genres as they go along. It might also have been the start of an intense conflict of interests between the creatives duo. In 2008 during a hiatus the artist Tanaka filled a 150 million yen copyright dispute against his writing partner Hashimoto claiming he was the true author of the series. Whatever happened behind the scenes resulted in a lengthy in Izo Hashimoto's name being removed from later volumes and Akio Tanaka being credited as the sole author from then on.
In any case the series does build haphazardly to a second peak with the Grand Cross arc. Mainly focused on a new rival for Ryo, the ballet dancer turned judo practitioner Touma Takahara. Probably also Tanaka’s peak in terms of artistic flexibility the ultimate showdown is worth enduring that very awkward set-up. This is also where Shamo, likely in an attempt to centre itself, becomes really obsessed with its main character being this unsolvable enigma who is drawing into his orbit who want to finally unravel his secrets. Which is completely removing the series from talking about the social issues it initially focused on. But it doesn’t come across as the author(s) egotistically praising themselves for making the best character ever. Touma’s obsession with Ryo’s evil is subtextual an attempt to reconcile his own repressed anger towards his own family and a previous failure to uphold his Christen values instead of a genuine and sincere belief. Making it an exercise in egotism instead of genuine compassion. Which does have some meat to it.
Unfortunately that is not the end of Shamo. It instead chooses to meander around for a few more volumes before an abrupt ending that leaves a great many things unresolved. Previously the series had been able to present situations where there is no emotional catharsis that still felt like there was a point to it. The final arc just feels like the fine gasp of exhaustion. Which is a shame. I do think Shamo is worth a shot if you like your sports dramas with a twinge of cynicism and a boatload of brutality. Just don't be like Ryo or his creators and know when to stop. If you think the series has lost its mojo then you're probably right.