Orphaned as a little girl, Azumi (Aya Ueto) is raised in the forest with a group of ten children by their master (Yoshio Harada), who trains them to be peerless assassins. Azumi and Nachi (Shun Oguri) are the strongest of the fighters. When the group comes of age, the master gives them one final test. He tells them to team up with the person to whom they feel closest. Then he tells them to kill that person, explaining that an assassin never gets to choose whom to kill. The teens reluctantly fight to the death. Then the survivors are brought out of the woods to begin their work, assassinating the corrupt warlords who are preventing peace in the land. The assassins, particularly Azumi, perform their missions with flair, but complications arise. One of the teens (Takatoshi Kaneko) is poisoned by a ninja's blade, one (Kenji Kohashi) falls in love with a circus performer (Aya Okamoto), and Azumi begins to question her desire to live the violent life of an assassin. Meanwhile, one warlord (Naoto Takenaka) cleverly escapes their blades, and together with his bodyguard Kenbei (Kazuki Kitamura) and a "monkey-faced" ninja, Saru (Minoru Matsumoto), they find Bijomaru (Jô Odagiri from Bright Future), a violent madman, release him from prison, and unleash him upon the young team of assassins. Azumi, based on the manga by Yu Koyama, is the first of cult director Ryuhei Kitamura's (Versus) films to be made within the Japanese studio system.