The white stroke gives a sense of movement and speed, and contrasts alot with the upper portion of the artwork, which seems so silent and still, with only the character's rather smug expression visible.
It looks like he is running through a canal or something similar maybe a irrigation ditch. I love how it looks like there is a large amount of water spraying up from his running motion, and the rocks and reeds on the ground, or so it loks to me ^^' All the black makes me think of GantZ and ninjas lol. Ah well I am a scatter brain after all ^^ and I love this !! Keep up the great work.