Better description:
The world was in terror when weird monsters came to reach havoc. But the hour of need the goddess descended giving the humans a chance to reclaim their world from the clutches of these terrifying beasts! The human society now ruled by the church, has an annual ritual where the youths, 16 years old, celebrate their coming of age. Everyone summons a holy weapon which shape stems from their own desires to take on the fight!
And Dongfang?, He just happend to summon a girl...