Granblue Fantasy

In a world where the earth floats in the sky, abandoned by the gods, a boy named Gran dreams of reaching the Star Island, Istalcia. One day, while training with his sword in the forest, a sudden thunderous roar echoed from the heavens. His village was under attack by the fleet of the Erste Empire!! As he rushed back, he encountered Lyria, a mysterious girl with blue hair and eyes. But imperial soldiers appeared before them, demanding he hand over the girl and thrusting their swords at him!!

(Source: Kadokawa, translated)