Yūji Endō (遠藤 勇次) is a dirty loan shark with ties to the yakuza. He lends out large sums of money to desperate individuals but charges absurd (and illegal) interest rates.
Tobaku Mokushiroku Kaiji
He tracks down Kaiji after a client of his, Furuhata, who disappeared without repaying a loan, which Kaiji cosigned in an act of weakness. Recognizing Kaiji could never repay the loan, Endō offers him the opportunity to board the gambling ship Espoir, where he would be able repay his debt and make some money as well.
After losing on the Espoir, he offers him another opportunity to pay back his debt by participating at the Starside Hotels gamble, not revealing what the gamble actually is. Sahara, wanting a chance to score big, pleads to Endo to include him with Kaiji.
After bringing Kaiji and Sahara to the event, he is not seen again in the arc.
Tobaku Hakairoku Kaiji
After Kaiji defeats Tonegawa his organization suffers because they now lack any connection to the upper management of Teiai.
After Kaiji is released from the underground labor camp and witnessing Sakazaki's failed attempt at beating the Bog, he goes to Endō for a loan to get enough money to pay for the equipment to beat it. He, Kaiji and Sakazaki form an alliance by signing an agreement contract.
Endō helps Kaiji borrow ¥50 million to beat the Bog and protects the Bog from being tampered with when it starts clogging up. Towards the end battle with the Bog, Endō loans Kaiji another ¥10 million at a very high rate of interest. Due to Kaijis desperate state he fails to read the contract he signed or the interest rate he agreed on.
After Kaiji's victory he drugs Kaiji one last time and takes the money he owed him, while expressing disgust toward Kaiji's pointless code of chivalry when he decides to split his winning to his friends in the underground labor camp. Despite his underlings remark of his cruel treatment toward Kaiji, he states that he could have robbed Kaiji all his money if he liked to but he still has his code of conduct and then takes only the amount of money Kaiji owned him.
With Kaiji's debt with him finally paid with an additional amount of money he had taken with his high interest rate, his connection with Kaiji is finally concluded.
Tobaku Datenroku Kaiji: 24 Oku-hen
After the events of the Bog, he now has a higher position in the Teiai Corporation having blacksuits now working under him. He has been assigned to track down Kaiji, Chang and Mario and the money they took from their gamble in One Poker.
During the manhunt, he is shown to be quite cocky as he thinks he can understand Kaiji's movement to easily catch him, Mario and Chang but fails multiple times as Kaiji outsmarts him.
Chuukan Kanriroku Tonegawa
He makes his appearance offering help to Tonegawa with the rehearsal of the newly created gamble; Restricted Rock, Paper, Scissors. Due to him misunderstanding the goal of Tonegawa, he only makes the situation worse.