Hoshin Engi, Vol. 1 by Ryu Fujisaki

[Viz] Betrayed by an immortal, trained by a God, hunted by Demons. When his clan is wiped out by a beautiful demon, young Taikobo finds himself in charge of the mysterious Hoshin Project. Its mission: find all immortals living in the human world and seal them away forever. But what is the ultimate goal of the Project? And does Taikobo even know whose side he's really on?! Armed with his new weapon, the Dashinben, Taikobo seeks revenge on the demon Dakki and her sinister sisters. He finds out much more about the godlike Sennins--and what may have really happened to his clan. But looking for survivors only means falling further into Dakki's darkness.