Reien Girls Academy

Kokutou Mikiya's sister, Kokutou Azaka's school.
A mission style all-girls academy. A sterile boarding school.
Originally it was a sister school of some seminary in England, but recently other girls academies had emerged using Reien as the template. The sponsor seemed to be Asagami Fujino's father.

Garden of sinners Pamphlet: Kara no Kyoukai Settings Glossary