Looks like Naruto. Only more mature and cool.
A sweet new shounen, have you read kekkaishi Gary?
Well there isn't anything graphic, not expecting much as well. But the dark sub-tones ring a lot, murder is not a light subject, and this kind of episodic murder, demons, mercenaries is not that far from a dark setting. Depends on the development really.
Holy shit, it's manga-Highlander!
Plus, there is a giant cool looking monster. :O