The story is set in a fantasy world of swords and magic, but this isn't a typical fantasy world since the technological progress have advanced so much that smartphones are everywhere!!

Everyone lives a peaceful life until one day a brother and a sister find a very strange sword.

(Source: MU)

Once upon a time, this world was ruled by beasts. Humanity no longer sat atop the foodchain, they are the monsters' prey. However, those who would stand up against the monsters gathered together and they continued to battle against the monsters in order to survive against their rule. Since then, hundreds of years have passed... and now the "fight" against the monsters has become the "hunt" for the monsters.