Rokka: Braves of the Six Flowers(2011)

Rokka no Yuusha

Seven heroes gather to save the world--but the legends spoke of only six. Long ago, the Evil God was sealed at the edge of the continent, where it lies in slumber. Each time it awakens, it threatens to plunge the world into hell, and each time, six powerful warriors are chosen to seal it away again. But now, as the cycle begins anew, the Crest of the Six Flowers marks not six Braves...but seven. Hans, the mysterious assassin for hire. Mora, the elder of the All Heavens Temple. Chamo, the young but deadly Saint of Swamps. Nashetania, the princess, and Goldof, the knight yearning to win her heart. Fremy, the girl with a dark past. And Adlet, the boy with a dream. When the Braves of the Six Flowers realize one of their number is an impostor, hero will turn on hero in this exciting new series!

(Source: Yen Press)