Zack Fair, from Final Fantasy VII and Crisis Core, will make an appearance in Kingdom Hearts: Birth by Sleep. Like Cloud Strife, he’s in the Olympus Colosseum. The scan from Shonen Jump shows Ventus and Zack as friends while Zack clashes with Terra.
When Terra (the character who looks remarkably like Zack) and Zack settle their differences they can team up for a Dimension Link attack called “Heroes Pride.” Dimension Link attacks are sort of like summons. You can link up with characters from other worlds, like Zack, for powerful attacks.
Seems fitting that Zack is in Kingdom Hearts: Birth by Sleep since it’s a prequel and Crisis Core: Final Fantasy VII is also a prequel. I wonder what other early Final Fantasy characters are going to be in the game. Maybe… the Warrior of Light from Dissidia: Final Fantasy?