This is simply a masterful expression of suspense.
While the visuals are fitting for this project, what makes this movie work so well is both the timing and the sound balance to create the necessary tension. The sharp, distinctness of both the sound effects and the music is what separates this from a standard horror project, as they immerse the viewer in a way the animation alone cannot. By building up the noises and the music in a careful manner, it makes the actual personified threat all the more frightening because it cannot be heard. At one time, the audience is "aware" of what the character is not but at the same time the audience shares his point of hearing (minus the music, of course), which grounds the viewer into him.
That is a very difficult balancing act to pull off, especially in animation, but this video shows it can be done excellently.