20世纪90年代中国东北,铁头(成龙 饰)和女孩秀秀(徐静蕾 饰)两情相悦。不久,秀秀作为二战遗孤返回日本,从此杳无音讯。挂念秀秀的铁头偷渡来至日本,投靠同乡阿杰(吴彦祖 饰),与一众华人偷渡客过着提心吊胆的黑工日子。 此时的秀秀已经更名结子,嫁给了日本黑帮三和会的若头江口利成(加藤雅也 饰)。亲眼见到这一幕的铁头心灰意冷,自此决心千方百计赚钱,留在日本。他们捞钱的手段很快触及到台南帮的利益,最终导致阿杰被斩断右手。铁头跟踪台南帮老大高捷(高捷 饰),意外得知一场黑社会的利益仇杀阴谋,他和一众朋友不可避免地卷入其中……In China, the poor worker Tietou repairs tractors and misses his sweetheart Xiu Xiu, back in Japan, she having never sent any news to her family or him. While illegally emigrating to Japan, Tietou loses his Chinese documents and so cannot return to his country. He is welcomed by his countrymen who lodge and work in Shinjuku where they also help him to find illegal work. While running from a police raid through the sewage system where Chinese are illegally working, Tietou saves Inspector Kitano from drowning in the dirty water. Later, after an incident with his cousin, Joe, and a Taiwan gang, Tietou saves the powerful Yakuza boss Toshinari Eguchi. He is the husband of Xiu Xiu, who is now called Yuko and are parents of a little daughter. The mobster offers a dirty job to Tietou; in retribution, he promises to deliver the quarter dominated by the Taiwan gang to him. Tietou becomes the boss of the Chinese illegal immigrants. But his peaceful methods make him unpopular and Tietou starts to lose control over his men which escalates into a giant gang war.