Only a pure maiden can have a privilege to make contract with a spirit.
In Areishia Acadamy, maidens from noble family were gathered there, giving them an elite education to become a spirit contractor. A boy Kamito, by accident he peeped on a girl, Clair, who was taking a bath, and he even made a contract with spirit that she wanted.
Kamito was actually an irregular male spirit contractor, which should not exist.
Seirei Tsukai no Kenbu
Spirit Elementalist’s Blade Dance
Vol 1-16 + Side Stories = EPUB/PDF
Vol 17 = EPUB