Mr. Miyagi travels to Boston, Massachusetts to attend a commendation for Japanese-American soldiers, who fought in the 442nd Regimental Combat Team during World War II. He meets Louisa Pierce, the widow of his commanding officer and a lieutenant, Jack. At Pierce's home, they catch up on old times and war stories.
Miyagi is also introduced to Pierce's granddaughter, Julie, a high school teen struggling with anger issues due to her parents' death in a car accident. Her behavior has led to friction between Julie and her grandmother, along with her fellow students and teachers. She sneaks into the school at night to care for an injured Harris's hawk, whom she names Angel, which she keeps in a pigeon coop on the roof.
Miyagi invites Louisa to stay at his house in Los Angeles to enjoy peace and quiet tending his garden while he remains in Boston as Julie's caretaker. At school, Julie meets and befriends Eric McGowen, a teenage security guard-in-training and a pledge for a shady school security fraternity, the Alpha Elite. The members are taught to enforce the school rules, mostly by using physical force, by a self-styled colonel, Paul Dugan. His toughest and most aggressive student is the short-fused Ned Randall, who makes unwanted sexual advances on Julie.
When Julie survives almost being hit by a car by jumping into a tiger position, she finally learns to confide in Miyagi when he approves of Julie's talent. She reveals that she was taught karate by her father, who learned from her grandfather, Miyagi's student.
Hilary Swank as Julie Pierce
Noriyuki "Pat" Morita as Mr. Miyagi
Michael Ironside as Colonel Paul Dugan
Constance Towers as Louisa Pierce
Chris Conrad as Eric McGowen
Michael Cavalieri as Ned Randall
Tom Downey as Morgan
Walton Goggins as Charlie
Frank Welker as Angel the Hawk (voice)
Arsenio 'Sonny' Trinidad as Abbot Monk
Daniel Inouye as Senator