Ultimate Survivor Kaiji (賭博黙示録カイジ, lit. Gambling Apocalypse Kaiji) is a Japanese seinen manga about gambling written by Nobuyuki Fukumoto, currently being published by Kondasha in Weekly Young Magazine. It currently consists of six manga series, with the sixth still in progress, and 65 manga volumes as of December 2017.
The manga begins focusing on a flat-broke young man (some may refer to him as a bum) in Japan named Kaiji Itou. After slashing the tires of a car, he's confronted by a man named Yuuji Endou, a loan shark who came to him because one of Kaiji's acquaintances had not paid of his loan and Kaiji had agreed to be his guarantor.
Seeing that Kaiji wouldn't be able to pay off the large debt of around 3.5 million yen due to his lack of funds, Yuuji offers to get Kaiji a place on the Espoir and gamble to get enough money to pay off the debt.