Seiken to Maryuu no Sekai

Seiken to Maryuu no Sekai summary:

The time is 10:00 pm, 24th December, the night of Christmas Eve. Proclaiming herself the Demonic Dragon Princess, the beautiful Ahrian declares war against the entire world. Her proclamation, subsequently know as the “Demonic Dragon Declaration”, completely altered the life of Kagari, who has always wanted to live a quiet peaceful life.
The city Kagari lives in faces an invasion by the “Six Imperial Demonic Dragons”. To defeat the Demonic Dragons, cute girls known as “Holy Swords” have also gathered in this city.
In order to protect this city as well as safeguarding his peaceful and quiet life, Kagari joins the Holy Swords in a struggle against the Demonic Dragons!
—- From Animesuki