St. Astraia Girls' School (
聖アストライア 女学院) is a combined middle and high school for girls of nobility and exceptionally rich commoners located in the Sankt District in Heimdallr, Erebonia. The girls attending St. Astraia reside in dormitories.
St. Astraia Girls' School has adopted the unicorn as its symbol. According to legends, these sacred beasts, pure white in colour with a single horn, are said to be capable of curing any illness and can only be touched by virgin maidens.
- Olivert Reise Arnor, Music Instructor
- Theresia Caroline signed up for Thors Military Academy in spite of her father's wishes to have her attend St. Astraia. Theresia opted for Thors because it offered a broader variety of sports clubs.