Based on

Movies like Mafia vs. Ninja (1985)

Sewage workers Jack and Charlie get involved in an international Asian gang war when Jack helps the boss of a Shanghai gang against one of his rebellious underlings. This underling then strikes a deal with the Japanese Yakuza in the hopes of toppling his boss and become the leader of Shanghai himself. When the Yakuza assassinate the Shanghai boss, Jack pledges to avenge his new friend's death. As he seeks out those ultimately responsible, he does battle with a variety of ninjas and mercenaries from around the world.