Ruri Aiba

Another main character of Sacred Seven. She is the daughter of a billionaire noble family who were killed by a Darkstone. She created Aiba Foundation to combat against the Darkstones. She is a Lightstone that has the ability to turn a crystal into a Lightstone and insert it into Alma to control his true powers. She became chairman of Alma's school (where she heavily renovated the school) to keep in contact with Alma. She has a twin sister named Aoi who also survived the Darkstone aftermath, but was crystallized. Her whole foundation is occupied with all female maids.

(Source: Wikipedia)