When Kiryu was young, his parents were murdered by a member of the yakuza. He ended up in an orphanage, and idolized Shintaro Kazama, the yakuza who operated the place. Kazama was a lackey of the Tojo Clan, who had been in a long turf war with the Jingweon Mafia. He was part of a plan to take out two of its leaders at a Christmas party in 1980, but had a change of heart, and tried to convince them to flee instead. Kiryu, misunderstanding the situation, tried to interrupt to save Kazama. In the chaos, a shootout ensued, Kazama killed the mafia boss, and many died.
In the years following, Kiryu’s obsession with the yakuza grew, and Kazama eventually allowed Kiryu and his pal from the orphanage, Akira Nishkiyama, to join the Dojima family.
But of course, Kiryu has to pay his dues, and so he starts on the bottom rung of the ladder…