Not much is known about Yuichiro's personality, but it is noted from Tokugawa that he is the complete opposite of Yujiro, implying that maybe he is a lot kinder than him, as shown when he supports Baki in the fight against his father much to Yujiro's anger. Also, Yuichiro seems to be a quite carefree and calm person. This may be considered as a one of the reasons why Yujiro is being so harsh on Baki since he reminds Yujiro of his own father.
There is evidence that shows he can be rather ruthless shown during the battle of Okinawa when Yuichiro is seen fighting and brutally beating the American soldiers in a most gruesome way ie. (twisted necks, broken bones etc.)
In the first chapter of Baki Gaiden: Kenjin it is revealed that Yuichiro wasn't afraid to lose prizefights for money. Doppo Orochi confronts Yuichiro about this, even saying he let his opponent trample on Japanese martial arts. Anyway, that makes him more benevolent than Yujiro since he tries to earn the money legally.
Yuichiro is a very large muscular man with exceptionally large broad shoulders noted by many not to be considered human. He has dark colored hair that he ties in a simple ponytail. Like many men in the Hanma bloodline he has the "demon" on his back muscles. Yuichiro also has cauliflower ears due to his grappling battles.
On the battlefield, he was wearing no shirt or footwear but simply dons on a pair of simple drawstring shorts.
Yuichiro is so strong that he was the only man before Yujiro to take on the full military might of the US with only his bare hands and win to the point where Major General James, the man in charge of the operation against Yuichiro requested for the use of a nuclear bomb just to kill one man when they were unable to control Yuichiro's rampage on a small island near Okinawa, when Yuichiro annihilated a platoon of soldiers unscathed even after the island he was on received heavy naval and aerial bombardment. Yuichiro then proceeded to kill Major General James on board the Iowa Battleship, throwing him with such immense power, his corpse pierced through the wood of the ship. When Yuichiro finally appeared before more than 2000 crew that gathered around their commander's corpse, all the crew scampered away from him with great fear and jumped from the ship towards the ocean, realizing that the person who stood before them was the man behind the death of all their fellow soldiers and their commander of the ship.
Baki Gaiden: KenjinEdit
Yuichiro met a disappointed Doppo Orochi, who confronted him about throwing his match against the pro wrestler Rikigouzan. Orochi knew fully well that Yuichiro is capable of blocking all of Rikigouzan's attacks and guessed that Yuichiro took the attacks because he could, and because his attacks were not even worthy of blocking. However, Orochi implied that Yuichiro trampled the pride of Japanese martial arts by throwing his match against Rikigouzan. Yuichiro, pleased by the fact that someone like Orochi knows his real capability, grabbed Orochi by his clothes, to which Orochi responded by nimbly getting out of the clothes Yuichiro was grabbing on to, and kick him to the jaw, possibly breaking it and declared that he will set things straight with Rikigouzan, which would then also clear Yuichiro's "loss" from Rikigouzan.
Above-Ground Great Quarrel of Father and Child SagaEdit
He appeared in the fight of Yujiro Hanma against Baki Hanma as a kind of spirit form. He shows up near the end of Baki’s climactic fight against his father, with the sole purpose of cheering on his grandson and giving Yujiro a hard time for having so much difficulty fighting against a kid less than half his age. His temporary visit is particularly jarring due to the series otherwise not containing any other explicitly supernatural elements. The interesting thing is that his presence seems to be so intimidating that even the inhumanly strong caveman Pickle can only tremble at the sight of him.
The true depths of Yuichiro's strength is still currently unknown, but those who've come across him suggest he is inhumanly strong. As such shown in the battle of Okinawa to be the only other man in the world besides his son to singlehandedly defeat the USA during WWII. It is unknown if Yuichiro is stronger than Yujiro, but there's speculation this is the only man Yujiro cannot defeat.
Yuichiro is only known to use one technique to defeat two thousand US soldiers on the battleship Iowa. Many of the soldiers call this technique "dress" only for Yujiro to correct it by stating the real technique was really called "guise" the user uses his opponent as a human weapon like a "nunchuku" surrounding himself in a spiritual image that looks like a dress. The power behind his throws are powerful enough that he is able to kill just about anyone he hits instantly, and is so immense, that when Major General James was thrown to the wood of the Iowa battleship, a wood durable enough to withstand direct attacks from big weapons, his corpse pierced through it. Furthermore, he can perform his variation of the technique so blindly fast that entire squadrons of soldiers can’t turn their guns fast enough to defend themselves against this truly gruesome move.
When Doppo Orochi started to fight him, he ends up possibly breaking Yuichiro's jaw. This hints that Yuichiro might in fact be weaker than his son (Yujiro tanked attacks way more brutal than a kick to the jaw without being harmed) However, it is unknown if Yuichiro simply let Doppo attack him as a way of testing Doppo's strength.
- The character is probably based on the real-life Japanese judoka and professional wrestler, Masahiko Kimura. To consider that Yuichiro was based on Kimura, it is quite possible that Yuichiro lost a prizefight on purpose to earn treatment fees for his ill wife.