The show uses the same characters as the show Mai-HiME but has a completely different setting although it does seem to be set after the events of Mai-HiME so is technically a sequel.
The plot is set in the distant future when humanity is leaving on a distant planet. In order to prevent wars and protect important people certain young girls are chosen and trained to become Otome. they are then infused with an old and mysterious technology that gives them Materialisation Powers (similar to those that seem to occur naturally in the girsl in Mai-HiME).
All in all this takes all of the good elements from that first show and removes all of the less than desirable elements making for a much better show.