Since high school, being late has been a common occurrence, and he has been immersed in pachinko and pachislot machines, as well as buying dubious strategy guides, upsetting his mother.
However, when he is put in an extreme situation where his life is at stake, he shows extraordinary courage, resourcefulness, and insight, and fights his way through the gambling hell with logical thinking and genius while having a "win because you must" mentality.
For this reason, he often talks about needing to dismiss others to survive, but he nevertheless tries to save those who have been cornered, even if it means killing off any chance at gain and profit for himself, which could be viewed as kindhearted by some and naive by others.
Afterwards, he sent Kaiji, who was seeking more gambling and still saddled with a debt that had grown to nearly 10 million, to the underground labor facility in accordance with Teiai's rule that there are no second chances.
In the live-action adaptation, he is changed to a woman named Rinko Endō, who is the head of a faction in the Teiai Group that is at odds with Tonegawa.
She loses the competition with Tonegawa and gets kicked off the career path, but she loans 50 million yen to Kaiji, who has spent all of his war funds on the E-Card battle.
Furthermore, in the final phase of the game, he is entrusted with rescuing Kaiji, who had fallen into the other room as a strategy to survive, but he was blinded by greed and incited Furuhata to back out of his promise.
Although he has not appeared directly in the story since the Ship of Hope arc, he has been burned into Kaiji's mind as a despicable traitor, reappearing in the flashbacks many times.
However, during the second race, Electrified Steel Beam Crossing, he is so scared of death that he cannot take a single step, so he entrusts his voucher to Kaiji to pay off his wife's debt instead.
A cunning man, he uses his experience of being a repeat participant on the Espoir to con others, such as scamming Kaiji out of two stars, leaving him with a single card and a hopeless situation.
The Balance Theorist (バランス理論の男, Baransu Riron no Otoko) (real name unknown), known as Hyena (ハイエナ, Haiena) in the anime series and Sugita (杉田) in the stage play adaptation, is one of the participants on the Espoir.
In the end, however, he is blown away and killed by a direct hit from the organizers' trap (a gust of wind caused by the pressure difference between the inside and outside of a skyscraper).
He is the main character of the spin-off series 1-nichi Gaishutsuroku Hanchō that takes place before the events of Kaiji, where he is depicted as a gourmet who frequently buys one-day outside passes to taste food and sightsee the outside world.
In order to get back together with his family, he plans to use 20 million yen in war funds to beat the Bog and runs into Kaiji, who has been temporarily freed from the underground kingdom.
After beating the Bog, he earns about 150 million yen and vows to quit gambling, choosing to cling tightly to the happiness of every day he can spend with his family.
He has a daughter, Mikoko, who looks just like him, but Sakazaki thinks she is extraordinarily beautiful and is on guard day and night to make sure she does not get any undesirable lovers.
He shows his talents numerous times, such as when he sees through Sakazaki's acting and quickly notices Kaiji's tricks and traps while the other casino members are unaware of them.
The live-action adaptation gives Ichijō additional backstory in which he is tricked by a friend into being a cosigner for a debt and sent underground, and that he is the survivor of the Brave Men Road (Steel Frame Crossing) gamble, like Kaiji.
In the end, his defeat caused a great deal of damage to Teiai, so he was sanctioned at Kurosaki's behest for 1035 years of underground labor and taken away from the casino.
A greedy, unmarried mammonist who believes only in the money put out in front of him, without the virtues and ideas of friendship and trust, he is determined to achieve a more solid success in every aspect of his life, and is willing to break the law to do so.
He hates risk, and has earned large sums of money by letting his subordinates (Maeda when playing against Kaiji) guide him with coded signs, as he does not want to go into a game unless he has a perfectly good chance of winning.
He also possesses a certain calmness and composure, as he remains neutral until the end of a game when judging a situation or watching from the sidelines, regardless of whether it involves a family member or stranger.
He then reveals to Kaiji that he detests the life he leads, and claims to not know true friendship or love, as everyone he meets kisses up to him due to the influence of his father.
Eventually, under the name "Kazuya Produce," he began to lure major debtors and sometimes classmates into gambling, with a prize of 10 million yen for the winner and the punishment of death for the loser, and he finds no issue in wasting money for his schemes, instead wanting to be an author.
He usually has a calm personality and can adjust to his surroundings despite having a bit of a weak side, but in the 2.4 Billion Escape Arc, he showed his courage and tact by snatching someone's bag on the spur of the moment in order to avoid being questioned by the police.
The trio vowed to complete the game, but in the final stages, Kazuya's machinations caused him to fall into intense disbelief, and in the end he chose the path of leaving Chang and Mario behind and winning about 70 million yen for himself.
In the 2.4 Billion Escape Arc, he runs into Chang and Mario at an apartment while picking up his belongings and tries to give them one million yen each as a parting gift, but his performative gestures and humanity is thoroughly reviled and scorned by them.
To stop Japan's rapid economic decline, he plans to implement a "deposit blockade" and use the people's assets to offset the national debt.
He has a fortune of 50 billion yen, but with little time left to live, he wanted to serve Japan as much as possible in his remaining life span, so he held a relief event.
He learns that the government is about to implement a "deposit blockade" and asks Kaiji and Kanako, the winners of the relief event, to help him gamble in order to stop it.