Kai -- at a certain point (after beating Konquest, MAYBE after training with everyone), you'll find Kung Lao at the Shaolin temple in earth realm. Beat him in a fight...he tells you to find Kai. Go find him in the Ice Caves in Outworld. He'll give you something (non-spoiler) and ask you to return to Kung Lao.

I saw Fujin in the Orederrealm, if that helps at all...he is in the center of the realm, and asks you to find a book for him, which is located in the outer ring of the realm in a house...

Yes but after you give him the book he says he will see you in earthrealm. so thats where we are with this problem