Mai-Otome

Summary
Arika Yumemiya wants to attend at the academy 'Garderobe'. This is a school were they teach girls to become 'Otome'. They have nano-machines in their bodies that give them immense strength. These nano-machines can be activated by the Otome's master. This shows the other side of being an Otome, you have tremendous strength, greater than any army, but you also have to be loyal to the lord or master you are appointed to. In international relationships, the amount of Otome's that serve in your kingdom is equivalent to your military power and thus your influence in the world. Being an Otome is a great responsibility that not everyone can bear. A lot of students in the academy will not make it to become 'Meister' Otome.
But back to Arika, who seems to come out of nowhere and makes her flashy entrance into the academy. She really wants to become an Otome and even more after she sees one of most important Meister Otome's in action. She turns out to be promising and makes new friends, but how did she get the necklace she has? And who is that strange female with cape and hat she seems to know?