Kōtarō Sakazaki (坂崎 孝太郎) is middle aged man, security guard and father whose daughter and wife left him because of his economical problems.
Tobaku Hakairoku Kaiji
He first encounters Kaiji in a dark alley way while Kaiji fends off several thugs by showing his cut fingers. Believing him to be part of the yakuza, they run off. Sakazaki however manages to see through this bluff and decides that he could be the person he has been looking for.
He explains he has been looking for a young gambler to help him to beat a pachinko machine called the Bog and win enough money to buy a house so his wife and daughter will return to him. At first he wanted Kaiji to help him beat the Bog but later he helps Kaiji defeat the Bog instead due to the plans Kaiji made.
Tobaku Datenroku Kaiji
After defeating the Bog, Kaiji moves in with his family later to be kicked out due to Kaiji slacking around in his house without working or contributing anything. However, one the reasons for him to kick Kaiji out was to prevent his daughter to get into any relationship with Kaiji as he finally sees as Kaiji is nothing more than a good-for-nothing piece of trash. Before departing, he gives Kaiji ¥3 million with Kaiji promising to pay it back after he wins at gambling but at the same time it also means that Kaiji will never return to see him and his family again.
Tobaku Datenroku Kaiji: 24 Oku-hen
He last appears when Kaiji finds him and repays the money he had lent to him with an additional profit due to him not lending the money, but giving it to him without any ties.
Believing Kaiji to be a fraud, he leaves in bad mood only to finally realize that he was wrong when he smells the some of the money Kaiji dropped at his doorstep in which he realizes the money are real. He chases after Kaiji and takes the ¥108 million profit from Kaiji while tearfully asking him to come back and stay with his family anytime he wants but Kaiji states that this is the last time they can see each others as he is on the run from Teiai. Repaying his debt, Kaiji leaves him behind while reminiscing about the time they spent together.
Chang later comments that Kaiji should not have given him such a large sum of money with Kaiji agreeing to this notion. He explains he gave Sakazaki such a large sum to act as insurance in case they get captured by the blacksuits in pursuit of them or if they manage to lose the money they currently have on them.
He is later being tortured by Endou with fingernail-piercing to get the whereabouts of Kaiji, Chang and Mario. Lucky for him, he is spared from further torture after the Blacksuits get a new lead about Kaiji, Chang and Mario's movement.
- He can tell fake and real money by smelling it.