Kokoro is an apprentice geisha that made her debut in Dead or Alive 4. In addition to her geisha training, she also studies the martial art ba ji quan. She gets permission from her mother Miyako to enter the fourth Dead or Alive tournament, though Miyako also says that she may meet someone close to her.
At the tournament, Kokoro encounters Helena Douglas, who to her surprise mentions Miyako by name. Kokoro doesn't understand how Helena knows Miyako, but in truth, Kokoro and Helena are half-sisters and share the same father, Fame Douglas. Unbeknownst to Kokoro, Miyako was one of Fame Douglas's numerous mistresses.
Dead or Alive 4
In Dead or Alive 4, Kokoro does meet some one close to her, just as her mother had predicted. During the tournament, she encounters Helena and begins to learn of her family ties.
In Kokoro's Dead or Alive 4 ending, she returns home to continue her training as a geisha.
Dead or Alive: Dimensions
In the Chronicle Mode of Dead or Alive: Dimensions, Kokoro briefly encounters Kasumi, who has passed out on a bridge with a fever while attempting to pose as a normal high school student. Before she can help her however, Ayane appears, and Kasumi flees. Ayane tries to get Kokoro to tell her which way Kasumi went, but Kokoro protects Kasumi by refusing, though Ayane subsequently beats her in a fight.
Dead or Alive 5
During the story of Dead or Alive 5, Kokoro is in Tokyo with her mother when she sees Helena's announcement of the fifth Dead or Alive tournament. She chooses to enter in the hopes that she'll be able to meet her again. Later, while practicing her forms, she has a chance encounter with Akira Yuki, who challenges her to a fight. She manages to defeat him.
Kokoro catches up with Helena at Taylor's Bar, located on the oil rig where the tournament is to take place, and asks her what sort of man Helena's father was. Helena tells her that he was a kind man, and that she's sure that Kokoro's own father was the same way, avoiding direct allusion to their sharing the same blood.
Ultimately, Kokoro makes it to the tournament quarter finals, but loses.