Fukuoka Prefecture is located in Southern Japan also known as Kyushu, which is home to five major yakuza groups with a total of roughly 3,000 members. Kyushu has been plagued by violent gang wars for nearly five years. The first violent conflict began in August 2007, when a shooter from the Kyushu Seido-kai crime group assassinated Yoshihisa Onaka, head of the Kurume City-based Dojinkai. In addition to inter-gang warfare, as the police have cracked down on organized crime in the last two years, local organized crime groups have reacted violently to efforts to curtail their economic activities. When gang members aren't lobbing grenades or shooting at each other, they are shooting at the offices of companies trying to cut organized crime Last year, on Nov. 26, Toshihiro Uchino, the 72-year-old president of Hakushin Construction --which was trying to cut ties to local gangs---was shot to death outside his home in Kitakyushu.

The most violent of the groups and considered the primary user of hand grenades is the Kyushu Seidokai. The Kyushu Seidokai has expanded into Tokyo, setting up several front companies, and joined forces with Tadamasa Goto, a former Yamaguchi-gumi boss turned Buddhist priest, who has now re-emerged as a powerful player in Japan's underworld. Tokyo Police are also worried that "pineapples" may be thrown around the metropolis in the near future. "A coalition between Goto and the Kyushu Seido-kai doesn't bode well for the public safety," said a detective who works organized crime. "We’re not excited about the possibility of yakuza lobbing grenades into Tokyo offices and homes."

So far, hand grenades have not been deployed in Tokyo.

Last year, the Fukuoka Prefectural Police released a large warning message on their homepage about a recent rise in crimes committed with hand grenades, while explaining the various types and how to best handle them. (Most Japanese people are not familiar with these tiny weapons of mass destruction.)

The homepage warns in large red letters that hand grenades are designed for killing people. It lists the dangers of being within a certain range of a hand grenade blasts and advises people that if they happen to see a hand grenade, “Do not step on it, touch it, or throw it,” and if you happen to see one to run away as quickly as possible. It also advises that if a hand grenade is about to explode, “hide behind something and protect yourself.”

The Japan Times reported in 2008, that in Kurume, Fukuoka prefecture, two years of gang war in the region had caused “seven deaths and more than 20 shootings and bombings.”

On April 10 of last year, two people were killed and 12 people were injured in the middle of the night in the city of Omuta, Fukuoka prefecture, as a result of a hand grenade explosion that occurred inside a car.