Seiken Densetsu - Final Fantasy Gaiden [Model DMG-FFJ]

Released on June 8, 1991 in Japan. According to Square's publicity department, the game sold 700,000 units worldwide, with 500,000 of these sold in Japan.

Square trademarked Seiken Densetsu in 1987 intending to use it for a game project subtitled The Emergence of Excalibur, and led by Kazuhiko Aoki for the Famicom Disk System. According to early advertisements, the game would consist of an unprecedented five floppy disks, making it one of the largest titles developed for the Famicom up until that point. Although Square solicited pre-orders for the game, Kaoru Moriyama, a former Square employee, affirms that management canceled the ambitious project before it advanced beyond the early planning stages. In October 1987, customers who had placed orders were sent a letter informing them of the cancellation and had their purchases refunded. The letter also suggested to consider placing an order on another upcoming Square role-playing game in a similar vein: Final Fantasy.

After the release of the third Final Fantasy title in 1990, Square offered designer Koichi Ishii to direct a spin-off series game. It began development for the Game Boy under the working title Gemma Knights; eventually, Square revived the trademarked name and released the game as Seiken Densetsu: Final Fantasy Gaiden. Ishii suggested the basis of the game's story, while scenario writer Yoshinori Kitase helped write the game's script. Ishii designed all of the characters himself, while Goro Ohashi was responsible for the development of the game system.

The Seiken Densetsu series, of which Final Fantasy Gaiden was the first game, was the result of Koichi Ishii's desire to create a fictional world. In Ishii's opinion, Mana is not a series of video games, but rather a world which is illustrated by and can be explored through video games. When working on the series, Koichi Ishii drew inspiration from abstract images from his memories of childhood, as well as movies and fantasy books that captivated him as a child. Ishii took care to avoid set conventions, and his influences are correspondingly very wide and non-specific. Nonetheless, among his literary influences, he acknowledges Tove Jansson's Moomin, Lewis Carroll's Alice's Adventures in Wonderland, and J. R. R. Tolkien's Lord of the Rings.

The Original Soundtrack was released on July 15, 1991 in Japan.

Two guidebooks have been released in Japan: Seiken Densetsu: Final Fantasy Gaiden kiso chishiki-hen and Seiken Densetsu Final Fantasy Gaiden kanzen k?ryaku-hen, each of which contains character illustrations and manga. The guidebooks were released in May 1991 and August 1991 respectively.