Short answers, pulled from the story.
The Mana series was created by Koichi Ishii, a designer at Square. Ishii directed the original 1991 Game Boy game and oversaw development of the World of Mana subseries before leaving Square Enix in April 2007 to found his own studio, Grezzo.
By 2021, the Mana series had sold over 8 million copies worldwide. As of March 2011 the total stood at over 6 million units. Secret of Mana alone shipped over 1.83 million copies worldwide.
The first Mana game was Seiken Densetsu, released in 1991 for the Game Boy. It was published in North America as Final Fantasy Adventure and in Europe as Mystic Quest. The original game sold over 700,000 units.
Secret of Mana is regarded as one of the best 2D action role-playing games ever made. It ranked number 97 on Famitsu's top 100 games of all time, and its music, including the opening theme Angel's Fear, has inspired orchestral concerts and remains among the most remixed video game soundtracks.
Hiroki Kikuta composed the Secret of Mana soundtrack, working largely alone and spending nearly 24 hours a day composing and editing. He aimed for two contrasting styles and considers it his favorite work. In 1995 he released a 50-minute arranged album from the game titled Secret of Mana +.
The World of Mana subseries was a Square Enix project announced in early 2005 that released four games in 2006 and 2007 across different genres and platforms. It included Children of Mana for Nintendo DS, Friends of Mana for mobile phones, Dawn of Mana for PlayStation 2, and Heroes of Mana for Nintendo DS.