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.
Attire wise he wears no shirt or footwear but simply dons on a pair of simple drawstring shorts.
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 one 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.
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.