- Danpei discovering that, as he was working his ass off to maintain and train Joe, the latter was running a scam and got in trouble with the law.
- Danpei having to beat Joe up so he could settle his debts with the law-and Joe's grudge over that.
- In juvie, Danpei apparently abandoning Joe in favor of training Aoyama. Sure, he was doing that to train Joe into both learning to defend himself and the solitude of a boxer on the ring, but it was hard on both of them.
- To help Joe and Nishi becoming professional boxers, Danpei worked incredibly hard to get the money for the Tange Boxing Club, stopped drinking, and generally straightened himself up so he could get back his licence... Then the day after Joe arrived he gets arrested for assaulting people while drunk, and when Joe and Nishi go at the police station to find out what's happening they learn that the Japanese Boxing Commission, composed by the directors of the other boxing clubs, has rudely refused to reinstate him due his past as a drunkard, mistreating his boxers, and assaulting opposing boxers, referees, JBC officials and even the public and openly stated he was hit in the head too many times if he thinks they'd reinstate his licence, and in grief he got drunk and then attacked them in a drunken rage, only confirming their beliefs.
- The fact the boxing club presidents, and especially Otaka of the Asia Boxing Club, used to be his friends, and the only reason they're not anymore is Danpei's own attitude as a boxing club president in the past.
- The fact the boxing club owners sincerely regretted having to take this decision, as that would mean that Danpei's two young promising boxers (that they didn't know yet) would never have the chance to live up their potential.
- This one gets worse after Joe forces their hand-and first Otaka instantly becomes his enemy for humiliating him, and after Rikiishi's death they start plotting to force him to retire for killing an opponent on the ring, an act heavily frowned upon in Japan even if it was an accident, and the terrifying defeats he's inflicting on his opponents ever since.
- Wolf Kanaguchi's story. When he first appears he's an up-and-coming bantamweight boxer believed to have what it takes to become the world champion and is about to fight for the title of strongest beginner bantamweight of Japan, he succeeds... And then, Joe punches him out for no other reason they're the same category and he needs to knock out the strongest novice bantamweight novice to get Danpei's license, and everything goes wrong:
- After weeks of fear of the Cross Counter, Wolf is taught the Double Counter to take on Joe in a match for the A-class license that would give him the chance to try for the Japanese championship, he succeeds in defeating the Cross Counter... And then Joe wins anyway with the Triple Counter;
- Joe's Triple Counter shattered Wolf's jaw, forcing him to retire;
- After he's forced to retire, Wolf is abandoned by Otaka, his manager, and thrown out of the Asia Boxing Club, without even a job. This is even worse because Danpei and Joe, who are directly responsible for his forced retirement, would have helped if they had the chance, and are appalled by Otaka's attitude;
- Wolf, his mind hung on the past glory, eventually finds a job as the bodyguard for a group of yakuza, getting the chance to use again the fists he trained so much for, on his first day he proves that, even if out of shape, he's still a force to be reckoned with, mopping the floor with ten opponents armed with knives... Then they come back with Goromaki Gondo, who kicks him in the jaw and inflicts on him a No-Holds-Barred Beatdown while he's holding the jaw in immense pain, forcing him to leave even this "job". And to rub salt in the wound, the one to stop the beating was once again Joe, himself depressed for killing Rikiishi... Who then recover partly due how pathetic Wolf had become.
- The death of Rikiishi. One moment, after their fight, Joe and he were about to shake hands in respect and friendship, then he suddenly collapsed with his hand still extended, and a few minutes later Joe was informed that Rikiishi had died of a brain hemorragy from Joe knocking him down with a temple shot and making him hit the ring rope with the nape of the neck. And right when their rivalry could finally end...
- It is especially poignant in one film adaptation, because it also included a BIG Hope Spot. Rikishi won fair and square, Joe acknowledged it and wasn't angry at all about that, and when both loser and winner were about to shake hands... BAM. Rikishi's brain damage kicks in, and he simply drops dead. Cue the Pastel-Chalked Freeze Frame and the narrator explaining what was going on.
- The effect it had on Joe was to almost ruin his career and life, three times over: first he put on a 10-Minute Retirement, and only came back due seeing how pathetic Wolf had got after being forced to retire, that and Yoko telling him he owed to Wolf and Rikiishi to come back on the ring and never retire as long as he could fight less he insulted their sacrifices; then Joe is so shocked by what he did that he's unable to seriously hit someone in the head, and if he forces himself to do so he'll feel ill; finally, the boxing club presidents making up most of the Japan Boxing Commission, incensed at Joe coming back on the ring after killing an opponent, decide to force him into retirement for good... And they catch on Joe's weakness.
- Another effect was to become's Joe's primary motivation to continue-to win everything he should have won. It's quite poignant when Joe goes through a terrifying diet to stay in the bantamweights and win the OPBF championship-and when he succeeds, he silently dedicates it to Rikiishi.
- Mikinosuke Shiraki abandons the boxing world, and would have sold the Shiraki Boxing Club had Yoko not decided to take it over.
- How Yoko took it. Rikiishi was a good friend of hers, and it's strongly implied that he was being groomed to become her fiance and husband, and he died at the hands of Joe, the man she loved (even if she didn't know it yet). She pretty much threw herself into parties to forget for a while, and then, to honor Rikiishi, first pushed Joe back on the ring, telling him he had no right to retire as long as he could fight, and then took over the Shiraki Boxing Club to both honor the man the club had practically been built for and guard over Joe... The latter done in ways that make the JBC think she's trying to kill him on the ring in revenge before an audience as large as she can get, and won't stop at anything to do so. A misunderstanding she's only too happy to feed, as it keeps the other boxing club presidents out of her way out of fear.
- The biggest reason she doesn't blame Joe is that she blames herself: she helped him with the diet, and when he was about to break it her actions, intended to make sure he did so in a way that didn't kill him, restored his resolve, leading to him keeping himself in his starved state for the match. That doesn't keep her from telling Joe to his face that, as the direct cause for Rikiishi's death, plus having forced Wolf to retire, he owes them to go back on the ring. The fact she caps the speech with the declaration that one day he'll die on the ring himself only becomes harsher in light of the ending.
- To make everything worse, this did not need to happen, and had things gone just a little bit differently in two separate occasions Rikiishi would have survived:
- At the end of the fourth round, Joe was almost out due a previous uppercut so powerful it broke Joe's tooth even with the mouth protector, and Rikiishi shot another uppercut-but stopped before connecting because the bell rung. Had that fist connected, Rikiishi would have won before the punch that killed him.
- Rikiishi was greatly weakened by a terrifying diet that brought him to the edge of starvation, and could have been saved had he not been so weakened he died in minutes and not in days (as had happened years before to a boxer who suffered an identical damage but had been in good health body). Shortly after the match, Joe went through a late growth spurt that made him almost as large as Rikiishi-had it started earlier, they would have been forced to postpone the match and then to fight it as featherweights, if not welterweights. And Rikiishi's health would have not been so bad.
- Yoko telling Carlos and Robert to leave with her during the match between Joe and Nango, as the current Joe just wasn't worth it.
- The wandering boxing troupe, composed of amateurs who can't get a license and has-been professionals down on their luck, all fighting fixed matches to entertain countryside crowds. At one point Danpei was part of one of these-and it's the one thing he's ashamed of. This is where Joe goes after how the fight with Nango ended gave the JBC club presidents the excuse to keep their boxers from fighting him, and where Inaba, formerly the #3 in the JBC featherweight rankings, ended after his prime.
- Upon finding out the fights are fixed, Joe starts punching the other boxers out, even as he goes easy on them, and is completely unrepentant about it... Then he finds out that most, if not all of them, have a desperate need for money for their families and can only fight, and that is why they fix the matches, so they can continue fighting, and making money, every single day without rest. But they can't do it if an angry professional wrecks their bellies...
- Carlos Rivera's story. Born in the slums of Caracas, he managed to come out thanks to his boxing skills, but at some point he had to spent periods playing the part of the weakling because his fame would otherwise scare away all opponents and leave him without a job, then he finally finds a Worthy Opponent in Joe and gets a shot to the World Championship... And Jose Mendoza, the World Champion, takes him down in one minute and thirty-three seconds. And he's got a severe case of punch drunk syndrome that forces him to retire, and according to his manager he got it from Joe's fists. He disappears soon after.
- How Carlos' defeat is revealed. Joe had visited Yoko to take the check for the fight with Carlos, he's about to leave when suddenly Yoko gets a telegram about the fight, her secretary announces the match has ended so quickly, Yoko is already cheering for his victory... And then the secretary explains that Carlos lost, much to hers and Joe's shock.
- Later Carlos reappears in Japan... Completely demented from brain damage, and in complete poverty. Yoko takes him in, hoping her medics can help him... And then it's discovered that while Joe gave him some minor brain damage, the one to destroy Carlos was Mendoza.
- The conflict between Danpei and Joe's over the latter's life-threatening diet to stay in the bantamweights, and his reaction when he finds out Danpei fixed the gym's scale to keep him from starving to death.
- Kim Yongbi's backstory.
- The anime-only part about the unification of the WBC and WBA belts has their own:
- To decide the first challenger, Joe is made to fight Leon Smiley, the highest-ranked contender for both federations, whose manager plans to make the thirteenth world champion he trained. After Joe wins by points, they become friends, Joe promises him that once he wins the title Smiley will be the first contender... Then Smiley pulls a joker from his card deck, is terrified by the bad omen and goes on a car ride to clear his head, but is so distraught he crashes and die. It's hinted that it was the sight of his body that made Joe realize his own mortality and that he'll die or have to retire immediately after fighting Mendoza.
- Shortly after the lineal champion's challenger is decided, Mendoza, WBC champion, fights Karold Gomez, WBA champion. Gomez gives Mendoza his hardest and longest fight to that point before going down, but Mendoza's Corkscrew Punches killed him.
- Yoko using her contract with Mendoza to force Joe to defend his title one last time so he'll reawaken his wild spirit and be ready for Mendoza while also giving her the chance to confirm or disprove his advanced punch drunk syndrome. It seemed their enmity was finally dying down, and then, like a puppeteer, she takes away his chance to fight Mendoza right when he's in a hurry before his punch drunk syndrome destroys or kills him unless he dances to her tune one last time, with many believing it's her final attempt at killing Rikiishi rather than trying to help him. Made worse in the anime, as there not only Mendoza himself wants to fight Joe as soon as possible, but Joe and Yoko had already become good friends and he did not expect something like that.
- In the last few volumes of the manga, the increasing hints that Joe is suffering from advanced punch-drunkenness. You can see how affected he is when he goes blind for a moment after tripping, as well as minutes later, when he can't even button up Carlos' shirt because his hands can't stop trembling. And then, right before the match against José Mendoza, he tells Yoko he already knew about his condition, yet he still plans to fight, which immediately puts this last match in a whole new light.
- The entire finale, where Joe dies.
- About that one, well... we all know what happened there. Not helped by how right before dying, Joe gives his bloodstained boxing gloves to Youko and tells her to keep them. Soon afterwards, Joe passes away; when Youko realizes that Joe is dead, she drops them in horror, and everyone starts standing up, and then we have the above image...
- Right after Rikiishi's death, Yoko told Joe one day he would die on the ring himself. Oh, boy...
- One part that isn't immediately realized is that, ever since his delinquent days, Joe had been planning to use his earnings to turn the slums in a decent place, building a factory to provide jobs at a decent wage, a hospital to care for the residents, and a school to teach the kids (that was the goal of his big scam, raise the money to start the project)... And now, he'll never be able to.
- Meta: those slums actually exist, complete with the Bridge of Tears (at least until that canal of the Sumida River was filled)... And while in real life the residents are able to use the connection to attract paying visitors and customers interested to the series (there's a few statues of Joe around and an entire shopping street was dedicated to the series), in Joe's world his death didn't leave such help.
Tear Jerker / Ashita no Joe
'The tomorrow that he keeps mentioning, that beautiful tomorrow promises something good... but that tomorrow won't be that beautiful forever. That tomorrow will be filled with blood, sweat, dust and wounds. For a weird guy like him... that meaning of tomorrow is... the real tomorrow!"
—Youko Shiraki, chapter 24