With Kingdom Hearts 4 somewhere on the horizon, speculation surrounding the upcoming Square Enix sequel has only grown. Once again focused on protagonist Sora, all that's known of the game is that it will be set in the strange, new "fictional world" of Quadratum. As the wait for Kingdom Hearts 4 has left fans searching for hints about the future in the series' past few releases, some characters have started to seem more likely to return than others.