Kairi lost his memory a decade ago and does not know what started his quest to fight. All he recalls is: "You must challenge your limits."
Kairi for some reason felt compelled to enter the fourth Street Fighter tournament. Though Kairi could not tell, he was being consumed by an evil entity known as Akuma. He learned this from a challenger called Hokuto, who turned out to be his sister. But Kairi didn't care and he fought, and in the end Hokuto was also possessed by Akuma...