Short answers, pulled from the story.
SaGa is a series of science fantasy role-playing video games developed by Square Enix. It originated on the Game Boy in 1989 and spans multiple platforms including the Super NES, PlayStation 2, mobile phones, PCs, and modern consoles. The series is known for open world exploration, non-linear branching plots, and unconventional gameplay.
Akitoshi Kawazu created the SaGa series at Square in 1989. Kawazu had previously worked on Final Fantasy and Final Fantasy II before designing Makai Toushi Sa-Ga, the first game in the franchise.
The first game was Makai Toushi Sa-Ga, released in Japan on the 15th of December 1989. It reached North America as The Final Fantasy Legend, borrowing that name to trade on the strength of the Final Fantasy brand. It was the first role-playing game on a handheld console and the first handheld game with a battery save feature.
The SaGa series sold over 9.9 million units as of March 2011 and surpassed 10 million units by 2019. Many individual games in the series sold over 1 million copies each, primarily in Japan.
Commentators have attributed the gap to the series' experimental gameplay, which offers open worlds with little narrative direction. This style was atypical of what many North American players expected from Japanese role-playing games. Official U.S. PlayStation Magazine specifically called out Unlimited SaGa in a September 2004 article, citing the game's troubled transition to the PlayStation 2.
Kenji Ito is the most prominent composer in the series. Nobuo Uematsu composed The Final Fantasy Legend alone and co-composed Final Fantasy Legend II with Ito. Ryuji Sasai and Chihiro Fujioka worked together on Final Fantasy Legend III, while Masashi Hamauzu composed SaGa Frontier 2 and Unlimited SaGa.