Ex-yakuza Old Guy gets conned in an "it's-me" emergency call scam. Get ready for the old-guy power, you punk fraudsters!
Ryuzo Takahashi is seventy years old. In the olden days, he was the head of a yakuza organisation and reverentially called "Ryuzo the Demon." But ever since he retired from the business, he spends his life of retirement rather timidly, living with his son and his family who treat him like a nuisance. With nothing else to do, Ryuzo frequently hangs out with his old-time buddy, Masa, moaning about how "the sense of duty and empathy" has been lost in this cold and cruel world.
One afternoon, Ryuzo receives a phone call while his family is away on holiday. The caller starts the conversation casually, "dad? it's me!" The call turns out to be a notorious "it's me" emergency call scam, which is currently one of the biggest social problems. Ryuzo completely buys the story and believes the caller is indeed his very own son Ryuhei. Scraping up what little money he kept and his most valuable possessions, Ryuzo rushes to the appointed place in order to grant his son's pleading to "prepare 5 million yen" so he "won't get fired from the company." Tamura, a self-proclaimed representative of the company who comes to meet Ryuzo, feels something intimidating about Ryuzo's demeanor and bolts right away from the site. Unbeknownst to him, Tamura belongs to a fraudulent organisation, which, ostensibly an IT upstart, but in truth, is involved in scams, extortions and rogue door-to-door sales and what not. The organisation is run by an ex-biker gang leader named Nishi who serves as the president.
One night Ryuzo and Masa bump into Mokichi, another old-time buddy of theirs, in the neighborhood shopping district, while he is being harassed by young street thugs. Detective Murakami, an old acquaintance of Ryuzo who works in the organised crime unit, intervenes and soothes the quarrel. They decide to have drinks together and there Ryzo learns that a fraudulent organisation called Kehin United is making a big money with emergency call scam. Infuriated by those free-wheeling punks who act as they wish, he summons their old buddies.
Gathering in front of the famous Takamori Saigo statue in Ueno are good old buddies whose looks have changed so much that it's almost impossible to picture them in the good old days. Mac the Quick Shooter has a revolver but he can't keep his hand from trembling. Ichizo the Cane Man has a cane-sword with a concealed blade but uses it to pick up cigarette butts. Hide the 6 Inch Nail now has to plod his way with unsteady steps. Taka the Razor Slasher just has his face marked clearly with razor burn. Yasu the Kamikaze still wears a Kamikaze pilot jacket stubbornly believing he's the last of the surviving Kamikaze pilots.
Their spirits are high as they get together and have drinks reminiscing the olden days. So much so that they decide forming their own organisation anew so that they can kick the crap out of those freewheeling punks of the Keihin United. They name themselves One Dragon League and Ryuzo becomes the boss of the family. The One Dragon League starts disrupting the Keihin United's fraudulent schemes one after another; seizing futon mats from a rogue door-to-door salesman who targets the elderly; interrupting their attempted defrauding from a food corporation, which has been accused of food-fraud and met with anti-fraud protest. The old guys are on a roll thinking they can still kick some serious butt.
Meanwhile at the Keihin United office, Nishi hears from his henchmen once too often about those "old farts" trying to cut in on their action. He decides to get rid of the annoying old farts once and for all. Nishi casts his eye on Yuriko, a grand daughter of Mokichi, who works as a hostess at a bar that Nishi runs. After hearing about Nishi's plan from his granddaughter and her man, Mokichi launches a preemptive strike on the United by himself, only to get defeated by his intended victim. With one man down and nothing to lose, old guys go about on their final mission to destroy their archenemy!