Created by Masahiko Takajo and Saruwatari Tetsuya, Riki-Oh is not for the faint of heart. It was serialized in the magazine Business Jump from 1988 to 1990 and later published in 12 volumes. The manga starts off very much like a weak Fist of the North Starrip-off however it eventually takes its own pace and voice after the first story arc.It is in the near future - sometime in the 1990s most likely - the world sucks, to say the least. Saiga Riki-Oh is in a privatized prison where Might Makes Right. He soon becomes an enemy of the Four Emperors, four powerful prisoners made head guards, and then the mysterious warden. The first storyline ends much the same way as the infamous "The Story Of Ricky" ends--BUT WAIT THERE'S MORE!Riki-Oh begins an adventure where he tries to find his brother, and find clues towards his past for it seems as though somebody is pulling the strings. Thus Riki-Oh's journal is full of combat where the action never ends. Bodies pile up as the super power martial artist punches and kicks through armies of freaks, robots, androids, monsters, martial artists, ferocious animals, and more!Very, very violent.
A Nazi by Any Other Name: The ultimate Big Bad, Ricky's father, and his high-ranking henchmen, are essentially just Nazis who use martial arts. And Riki's own brother, "Nachi" is a deliberate pun n the word "Nazi". He even has a swastika tattoo on his hand.
And Now For Something Completely Different: There are roughly five story arcs in the manga: the Tokyo State Prison arc (chapters 1-13), the Cape arc (14-30), the Return to Tokyo arc (31-41), the Palace of Eternal Youth arc (42-62) and the Antarctica arc (63-75). The Prison Arc has some weird stuff but it's mostly weird martial artists. Then the Cape has some of the weirdest stuff, from elephants to "power readings", to android workers, to cyborgs, to an underground fighting arena, with the big bad being a super psychic. The third arc tones it down and has a more noir feeling with villains more like super-powered freaks than martial artists. The final two arcs are when things truly get insane. Each arc different? Yes. Each Arc awesome? Yes.
Charles Atlas Super Power and Made of Iron: Oh so many. Buried alive for a week at one point; when he was unearthed, he effortlessly shattered his chains and somersaulted to his feet. He also had his arm sliced, and stitched it mid-fight without being hampered by the injury at all. Overcame an instant-death technique through sheer willpower. After defeating the big bad, he single-handedly put a massive hole through the prison wall and walked to freedom.
There's more. The arm slice cut his tendons, which he tied back together. He's stitched his own wounds with a length of a chain link fence.
Crapsack World: In a world where Tokyo cannot be repaired from earthquakes, heavy depressions all over the place, wild gangs, drugs are everywhere, chemical and nuclear waste is unchecked, and worse - there's a powerful hidden group of upper class that is TRYING to destroy the world. Believe it or not, there is still hope.
Cursed with Awesome: Sure Riki-Oh may hurt his family but he gets to punch people's brains out!
Expy: Saiga Riki-Oh is basically Kenshiro by a different name.
M. Bison/Vega from Street Fighter is an expy of the villain Washizaki, who himself is an expy of the Big Bad Yasunori Kato from Doomed Megalopolis/Teito Monogatari.
Umibozu, a fat Giant Mook who appears at the of Vol. 3, is the manga's version of Mr. Heart from Fist of the North Star (only taller), right down to his ability to absorb Riki's punches with his fatness. Riki-oh is even forced to defeat Umibozu the same way Kenshiro defeated Mr. Heart; by using a technique which slices through flesh.
The Disciples of the Wolf Commandment are a gang that patterned themselves after a pack of wolves, just like the Fang Clan also from North Star.
there is a Giant Mook that is Conan the Barbarian, the mech from RoboCop with Deadlock from the ABC Warriors rideing it
Full-Frontal Assault: Mukai in his first confrontation with Riki. This would be the "unconcerned with human expectations" variety, not the "raging primordial beast" variety.
My Own Grandpa:It turns out that Mukai, Riki-oh and Nachi's father, is an artificially bred man-god from the year 2500 who was created by one of Riki-oh's descendants.
Monster Clown: One of the elite mooks at the Palace of Gold dresses as a clown and gets to pummel Riki-oh a little.
Omnicidal Maniac: As it turns out, Mukai was inciting just about everything—even some of the historical atrocities throughout the earlier part of the twentieth century—in an attempt to obliterate humanity. As to why he's doing this...because of the religious fanatics who bred him to begin with, he believes that God erred badly in creating a physical, independent humanity in the first place. He believes the only way for paradise to be restored is to reduce humanity back to a strictly spiritual form so they can merge back with God. Long story short, Mukai believes God should never have created anything in the first place, because anything other than eternal stasis was doomed to compromise perfection.
Person of Mass Destruction: When Riki-Oh and Nachi touch their marked hands together, it creates a natural disaster, i.e. tornados, earthquakes, tsunamis, etc.ù
Artistic License - Biology: Many, many examples. Notable ones are a mook still talking, and trying to kill Riki-Oh after having his brain punched away, and another one being completely operative after his heart was torn from his chest, with seemingly no ill effect, only to die immediately when Riki-Oh finally crushes the heart, still in his hand. It should be noted that this is not even handwaved as magic or superpower. It just... kinda happens.
You Fail Religious Studies Forever: Apparently the swastika is a symbol for atheism and the six-pointed star is a symbol of theism. Oh, and they also represent the universe collapsing and exploding into existence respectfully (destruction and creation). Oh, and God gave the world 6000 the years, and if the Earth isn't destroyed year 2000, it means "his plan" didn't succeed according to the Holy Bible. There are just so many egregious examples of the manga not doing the research on Christianity that it's almost hilarious. It doesn't even get the message of the "sacrificing of Isaac" story right.