Nachi's backstory. Despite how he turns out, the circumstances behind Nachi's abandonment by his brother are heartbreaking.
The child Riki-Oh was friends with, (Mizukami Keiko), was part of the reason he came to the JP compound. A drug-pushing gangster named Kuwabara caused her to become comatose. What happened to that little girl was truly heart-rending...
A prison-dwelling boy who admired Narumi of the "Four Emperors", was skinned alive by another of the group, Yomi. And Yomi never received retribution for it.
Later on, Riki-Oh meets up with his adoptive father, Saiga Michiomi. He is forced to lay the old man to rest a little later.
The big ape-man, Eisaku, who was an enemy at one point, sacrificed himself for his friend's survival. He still had a mother too.
The way everything ended up after "The Cape" chapters. It seemed like Robo-tomi, Schteiner, even the girl he was in a love triangle with the previous guy, everyone else died. No wonder he ended up like he did afterward, seemingly a shadow of his former self.
There is a rather long scene later on that takes place in the WWII era, largely featuring Aneyama and Zenki, among others. It really shows how chilling a human Aneyama is, as it shows Michiomi's father being tortured. The incredible pain he must have endured was so horrific, it can make someone shed a tear for the guy.
The mere fact that unlike Kenshiro, Tsurugi Momotaro, or any of the Joestars, Riki-oh has no actual consistent travelling companions give the entire manga a bizarre melancholic feeling due to how alone Riki-Oh is.
