Japan's largest yakuza group
The Yamaguchi-gumi was founded in 1915 in Hyogo prefecture, western Japan. It expanded significantly from the late 1950s to the early '70s, becoming the most powerful yakuza gang in Japan.
The year 2005 proved to be a pivotal one for the group, as two new leaders took charge. Shinobu Tsukasa became the head. Kiyoshi Takayama controlled the finances and ran day-to-day operations.
Both were originally from a branch of the gang based in Aichi Prefecture, and some members felt that the new leaders were biased towards their old group. Soon, a majority of the senior bosses were from there, and they brought with them a style of operation that was stricter than many members were used to.
But in 2014 Takayama was arrested for extortion and sent to prison. That's when things started to change for the syndicate.
In 2015, thousands of members broke off and formed a rival gang, called the Kobe Yamaguchi-gumi. Then, two years later, the new group fractured and spawned a third syndicate, the Ninkyo Yamaguchi-gumi.
Feuds between these gangs have resulted in more than 130 violent, often headline-grabbing attacks. In one case, a gang boss was stabbed in a shopping mall. In another case, a gang member was targeted in a drive-by shooting.
The escalation of a feud
Takayama was released from prison this October, and it only served to exacerbate the tensions.
One person close to the Yamaguchi-gumi told NHK that gang members are taking on the splinter groups in an effort to unite their syndicate under Takayama.
"I think Takayama firmly believes the syndicate wouldn't have splintered if he'd been around," they say. "There's a tension now as he's making changes, dismissing or demoting some of the members."
Atsushi Mizoguchi, an expert on crime syndicates, says he thinks the fighting will continue, because Takayama wants to take it all the way to a clear conclusion.
Anxiety in the community
People in Amagasaki are still in shock over the violent murder on their streets.
An elementary school near the scene now has police guards, and volunteers are patrolling in the daytime.
One woman says her terrified child is asking whether the criminal has been arrested.
Cracking down on the yakuza
Japanese police are now considering designating the Yamaguchi-gumi and Kobe Yamaguchi-gumi as gangs that can bring serious danger to people's lives.
The designation would make it illegal for five or more members to gather or to pursue members of a rival group.
The question in the minds of people living near yakuza activity is whether these new restrictions would be enough to keep them safe if the war continues.