Reiko's Prologues

Tekken 4:

"Reiko is the younger sister of Jin Kazama, with a gap of two years between them. When she was young, she was unable to protect herself, thus having Jin backing her up. Though grateful, Reiko felt envy growing within her due to her sibling's skills. One day it all changed, however, her mother - Jun Kazama - informed her she is going to meet her father.

...

In the age of 10, she was sent to G corporation's headquarters in Nebraska, where she met her father - Kazuya Mishima. She was stratled by his intimidating presence first, but slowly warmed up to him, and suprisingly, her father did the same to her. Realising she might have his skills, he began teaching her Mishima-style karate, and became a master of the family's martial art at the age of 15.

...

Her peculiar fighting abilities, along with the Devil Gene rapidly evolving within her, turned the fragile young girl into a formidable and dangerous fighter. 7 years later, Reiko and Kazuya went to G corporation to find the GENOCELL data, which contained information about Kazuya's biological research. However, the two have been ambushed by the Tekken force, but they managed to defeat them all and escape with the data.

...

Reiko decided to find about the ambush, and decided to find her grandfather: Heihachi Mishima, the leader of the ambush. Realising that her brother might also enter to solve the mysteries behind their bloodline, the young girl simply smirked. Now it's her time to prove she's better than him in any way"

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Tekken 5:

"Reiko Mishima, the daughter of Kazuya Mishima, and the only female devil in the whole bloodline...

After Jin flew away from Honmaru, Reiko, Kazuya and Heihachi were ambushed by JACK robots, sent by G corporation, to eliminate Kazuya.

...

After a fierce battle, Kazuya threw Heihachi to the robots and ecaped along with Reiko. While Reiko watched the exploding temple with Heihachi within it, she noticed a man in the shadows, watching her as she and her father flew away.

...

Reiko decided to enter the 'King of Iron Fist' to find the man and the information she needs about the true goals of G corporation. 'Father, it's time to show my skills and find what we need for better times!', said Reiko."

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Tekken 6:

"Reiko joined her father, Kazuya Mishima, in the King of Iron Fist 5 to find information about Heihachi's 'death', and about the assassination at Honmaru.
After the two gathered the information they needed, they went to the G corporation main headquarters in Nebraska, and with Reiko's hacking skills, they've crossed the security system and killed the workers responsible for the assassination, and took over the company.

...

Becoming her father's top enforcer and ally, Reiko proved her skills and soon enough G Corporation was praised for fighting against the Mishima Zaibatsu, seen as heroic in the world's eyes. However, for Reiko, reputation wasn't enough. When Jin announced the King of Iron Fist Tournament 6, Reiko quickly prepared herself with intense training. She was willing to take out Jin, and for good, in her father's name and sake."