Miss Mirimoto

"Once the Black Samurai has returned, I will order him to lead my robot ninjas against the ignorant forces of this modern age. Then the ancient world of the samurai and the new world of technology shall exist in perfect harmony."

- Miss Mirimoto revealing her plan to the Mystery, Inc. gang

Miss Mirimoto is the hidden secondary antagonist of Scooby-Doo and the Samurai Sword. At first she didn't look or act like a villain but later she revealed her true colors. Once her true colors were revealed, she was though to be the film's main antagonist, however she was eventually overthrown by the movie's true main villain.

Scooby-Doo and the Samurai Sword
Miss Mirimoto is a powerful sensei who runs a karate academy with an iron fist.

When Scooby-Doo, Shaggy, and company take Daphne and their new friend Miyumi to a martial arts tournament, Daphne takes down Miss Mirimoto's sturdy bodyguard, Sojo, and is congratulated by the sensei herself. Miss Mirimoto tells Daphne she shows promise as a courageous warrior. Mr. Takagawa, a museum curator, explains to her that the dreaded Black Samurai is after the Destiny Scroll, which is at the academy.

That night, the Black Samurai and an army of ninja warriors break into the school and steal the scroll. Miss Mirimoto explains that it's just a copy and shows Scooby-Doo and his friends the real one.

Later, Miss Mirimoto instructs the gang to find the Sword of Doom before the Black Samurai does. After finding hte sword, they discover that the Black Samurai is Sojo in disguise and when they bring him back, Miss Mirimoto, aided by Miyumi (who turns out to be one of her students) takes them hostage. She tells them of her wicked plan, which is to bring the Black Samurai back to life so she can use him to bring Japan back to the way it was in ancient times and destroy the modern world. The ninjas are revealed to be robots in which she channeled her students' fighting techniques (including Daphne's). Miss Mirimoto holds Daphne, Fred, Velma, and Mr. Takagawa prisoner, locking them in the museum, but not before Daphne throws the sword to Shaggy and Scooby-Doo, who escape and, aided by a green dragon, charge to the rescue.

The friends are rescued by Kenji, the janitor. In the final battle, Miyumi takes the Sword of Fate, turns against Miss Mirimoto, and fights her before the evil woman succeeds in taking the sword back. However, Miss Mirimoto tries to make the Black Samurai her servant, but the true lord of evil mocks her for even thinking she could control him and tosses her against some stone steps.

Quotes
"Welcome to Mirimoto Academy's Tournament of Champions. The finest martial artists in all the world have gathered here today for one single purpose: To prove they are the best." - Miss Mirimoto welcoming the students

"Tomorrow night, when the moon is full, I will resurrect the Black Samurai from the sword of doom. Once I have freed his spirit, he will call me master." - Miss Mirimoto before she captures Daphne, Fred, Velma, and Mr. Takagawa

"How dare you disobey me!" - Miss Mirimoto furious that Miyumi has taken the sword and when she attacks her

"I am the master here. Bow before me and I will give you the world." - Miss Mirimoto ordering the Black Samurai to aid her

Trivia

 * Miss Mirimoto is voiced by Kelly Hu, who also voices the heroine Miyumi.
 * She has some similarities to Nurse Ratched.