Seirei Tsukai no Blade Dance

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 an accident he peeped into a girl, Clair, who was taking a bath, and he even made a contract with spirit that she wanted.

Kamio was actually an irregular male spirit contractor, which should not exist.