Near the end of the second tournament, Kei Ikushima, after defeating Regulus in the finals, discovers that the underground laboratory's self-destruct mechanism has been activated. As she was about to make her escape, she would end up crossing paths with Eileen A. once again.
Kei tried to escape the lab with Eileen, but she hesitated, instead telling Kei the answer she was looking: Kei was actually the daughter of none other than the CEO of Orion Corporation, Ranzou Kihara. She then gives Kei a letter before telling her to go on and leave the building without her. Kei hesitates at first but soon obliges as the lab eventually explodes, leaving Eileen behind, her fate unknown.
Three years after the explosion at the Orion labs, Kei finds out more about her past from the letter Eileen gave her before the incident. She also found out that her DNA was taken for usage in Orion's Perfect Fighter Project, the very same set of experiments that orphaned her adoptive father Shin and ruined the lives of many others.
Fast forward to several weeks before Kei’s 20th birthday, several attacks on various martial artists have been reported. All of them perpetrated by people who bore a striking semblance to Kei. As a result, Kei has been blamed for all the attacks, despite having no hand on them. Kei then began to suspect that it had something to do with the Perfect Fighter Project that Eileen had mentioned.
Then, on the day of Kei’s 20th birthday, Orion announces the third Sentoki: Global Martial Arts tournament. Kei joins the tournament in order to cleanse her name and find out the truth of it all.
