Allies: Liu Kang
Like Liu Kang, Kai is a Shaolin monk and member of the White Lotus Society. During the events of Mortal Kombat 4, Kai meets Liu Kang in America and trains under him to gain the title of Shaolin warrior. After discovering that a fallen Elder God named Shinnok has returned and captured Kitana, Kai and Liu Kang join the rest of the Earthrealm warriors in Edenia with Raiden to battle Shinnok.
After defeating Shinnok, Kai goes on a spiritual journey, pledging to wander the Earth until he feels he has reached enlightenment. As a sign of thanks and to help him on his journey, Raiden gives him his lightning staff.
After defeating Blaze, Kai finds himself psychically linked with Old Being. Taking the opportunity to better his knowledge, Kai goes into deep meditation and searches through the realms of the Old Being, an entity who is responsible for reality itself. During his meditation he witnesses several things, such as Shao Kahn's rise to power and his defeat by Liu Kang. When Kai looks to the future for knowledge, however, he sees nothing.