Loved It.
Wish it was longer, and I'm extremely curious about the story, but these are both just signs that it was really good. The song isn't really my type of music, but it fit the animation, so no complaints there. I want to suggest adding voices, but really that's a pretty big addition were you to make it, because poorly cast voice actors could conceivably ruin even a great work such as this.
That aside, this is a very stylish animation. The designs, and plot were reminiscent of MegaMan Legends, which in my eyes is a good thing. I hope you're planning to make a series of this, because I want to see more.