The scene where Kumiko greets Daniel and Mr. Miyagi and the scene where Kumiko picks up Daniel for the 50's dance

I don’t think authenticity is a huge concern for the filmmakers. They filmed ‘Okinawa’ in Hawaii, and the actor playing the villain was Hawaiian, plus most of the karate moves and techniques are bullshit. Notice also how everyone in ‘Okinawa’ speaks to each other in broken, stilted English.

Kumiko’s kimono is the least of the film’s credibility problems.