The Karate Kid Part II
Kumiko is the niece of Yukie, Mr. Miyagi's childhood girlfriend. She dreams of becoming a dancer and falls in love with Daniel. She was first seen teaching little girls how to perform the O-bon dance, which was a Japanese way of honoring the dead. She later shows Daniel how to perform that dance, but this is sighted by Chozen and his underlings, who mock Daniel for being girly.
Later, when Daniel is in the city of Naha, Kumiko is also there to buy a refrigerator motor for her Aunt Yukie. As they are walking by an electronics store, Yukie shows Daniel what she wants to be. Daniel first asks if she wants to be a TV saleslady, to which Kumiko says no, as the TVs were showing a ballet; she meant she wanted to be a ballerina.
She shows Daniel that she cares for him by performing a traditional tea ceremony with him and accepting his offer to come with him to the United States, likely thinking there would be great opportunity for her in America. At the film's climax, the O-bon festival is being celebrated in Sato's seaside castle. Kumiko is performing a dance for all the partygoers are on a small islet when is captured by a crazed Chozen who threatens to kill her with a balisong knife if Daniel does not fight him to the death in an honor match. Daniel accepts the challenge, despite calls from Sato for Chozen to stop his behavior and a warning from Mr. Miyagi that this is not the All-Valley Karate Tournament, but Daniel says he must accept the challenge as Kumiko is in danger.
Chozen has the upper hand earlier in the fight and badly beats Daniel, causing Kumiko to attempt to stop the carnage by not being afraid to stand up to Chozen herself, only to be knocked unconscious by Chozen. When Sato and the partygoers play their drums in rhythm, Daniel, despite on the verge of losing, manages to defeat Chozen with Mr. Miyagi's "Drum Technique". Chozen instructs Daniel to kill him so his honor can remain, but Daniel refuses to do such a thing and spares his life before honking his nose. This humiliates Chozen, who leaves in exile. Kumiko and Daniel embrace as Mr. Miyagi smiles at Daniel.
The Karate Kid Part III
Daniel's mother enquires about Kumiko and Daniel explained that she was offered her dream job at a ballet company in Tokyo. As Daniel wanted her to follow her dreams and be happy more than he wanted her to be with him, he reluctantly convinced Kumiko to stay in Japan and pursue her dancing career.
When Daniel's daughter Samantha is upset over her breakup with Miguel Diaz Daniel tries to console her by telling her about his past girlfriends. When Sam asks what happened to his relationship with Ali Mills he refuses to tell her and instead says "That's a story for another time", "And there's a story after that one", with the latter statement most likely referring to Kumiko as she dated Daniel after Ali.
It has been confirmed that Daniel will be going back to Okinawa, meaning that Kumiko will likely make an appearance.
- Kumiko is the only love interest in the films who helps Daniel defeat the main antagonist.
- Kumiko is the only love interest in the films whose life is threatened.
- Kumiko and Daniel would have remained a couple if it weren't for the fact that he wanted her to follow her dreams back in Japan.