

When he first meet her in the Maximum Tournament, he flirted with her, although he might have only done this to provoke his brother. Jack also seems to have some feelings for his younger brother's girlfriend, Kozue. He also has perfect table manners and sometimes feeds the koi with little old man Tokugawa. He learned to calm down and grow friendlier towards others. Following his defeat at the hands of Baki, he became more humble and amicable towards his half-brother. He sees his brother, Baki Hanma, as a rival, but also likes and cares for him deep in his heart as they have the same goal in surpassing Yuujirou. He almost out-savaged Pickle during their fight and the caveman came to see him as a wasp, the only creature he fears. Jack can indeed seem very frightening to his enemies: for example, he startled Pickle after Jack lost to him, because there is nothing in the wild that prepared the caveman to the sight of a prey seemingly coming back from the dead for a rematch. He refuses to hold back against his opponents and, speaking of behavior, he prefers to act like a wild animal rather than a true fighter, as especially shown how he bites his opponents during their fights, making him even more animalistic. He doesn't know many techniques and often fights head-on. He is too obsessed with beating Yuujirou and avenging his mother, to the point where he is blinded by that dream.

He trains too much for his body to handle, forcing him to resort to steroids and other medical methods in order to keep his strength growing steadily.

Also, it can be said that he is sometimes too confident in his strength. Even having half his face bitten off by Pickle and waking up in the hospital twice, the second time from a severe coma, he still gets up and goes right back to it. He's had his skeleton surgically restructured multiple times to get bigger. His overtraining would be suicidal, if not for a mad scientist's steroid cocktails being part of his regimen. Jack is an incredibly determined and stubborn person he just doesn't know when to quit. After taking super steroids that made himself beyond unstable, Jack turned into a monster without balance who only cares about becoming stronger to take revenge. Jack's driving force is wanting to defeat his father, Yuujirou Hanma, to avenge his mother who was raped by him.
