In 1604, Miyamoto Musashi attacked the Yoshioka family at their dojo and defeated master Seijūrō and his younger brother Denshichirō in two duels. To save their reputation, the Yoshioka family decides to fight back with all 100 family members and hire an additional 300 samurai. Now Musashi sets out to defeat all 400 enemies in his most famous battle.
In Ikebukuro, unbeaten street fighter Ran Sakurai (Yosuke Kawamura) and his friend Kenji (Yosuke Asari) run a benriya operation called "Randys" to earn enough money to buy a haka for their dead friend Shinichi Hoshi (Tsutomu Takahashi). Randys is named after their hero, Randy Bass: the American baseball player who helped lead the "hard luck" Hanshin Tigers to a Japan series title in 1985. A benriya is basically a problem-solver that accepts payment to do anything you need done, and Randys specializes in helping the weak triumph over the strong, much like Randy Bass did with Hanshin. One day, they find out the feared leader of a team of badasses called (appropriately enough) the Giants, Takeshi (Hisato Izaki), has returned to Ikebukuro to stir up trouble. He has only one goal: to beat the crap out of Sakurai. A dispute that began 4 years ago is about to be settled, but not before the streets of Ikebukuro are covered in blood...