Joe Hayakawa (ジョー・ハヤカワ, Jō Hayakawa?) is the father of Yu and Ai, and husband of Mary Hayakawa in Final Fantasy: Unlimited. His wife and he became famous after they journeyed into Wonderland to conduct experiments, publishing their findings in a world famous book, "Day of Succession".
Joe and Mary are among the first characters seen in the series; appearing the first episode, Wonderland: Journey into the Darkness, observing the Pillar of Darkness forming. Some time after, the couple decided to venture into Wonderland to search and study the new world.
During their visit they discovered many things and conducted a grand amount to research, concluding that the law of physics vary between the world, and published their findings in the aforementioned book. However, their most prized findings was not information, but a pair of human like children. Seeings as Mary had recently lost their own children, the couple adopted the pair, naming them Ai and Yu, and raised them to believe that they were normal children.
Twelve years later the couple decided to return to Wonderland to compile data for a second book, but were captured by Herba and Earl Tyrant, and brainwashed into assisting them by creating meals from negative emotions. Their absence prompted the C2 Organization to dispatch Lisa Pacifist to return them to Earth, and Ai and Yu to search for them on their own.
Though they were freed from the Earl's control during the series's climax, they ended up in the hands of the C2 Organization. The two were held in London until Kaze arrives to fight Soljashy while destroying C2's base. The two escaped in the crossfire thanks to Natalia Bornakov.
- Both Joe and Mary, despite being Japanese, have noticeably Western names. However, it is likely the couple's name is a reference to Mary and Joseph, the Earthly parents of Jesus Christ. This is somewhat fitting, considering that this couple comes to care for children that would save Wonderland and defeat Chaos.