I like the music, the graphics and the general aesthetic... but the controls are just bad. When moving enemies are on relatively narrow platforms, attacking mid-jump should be something you can do without reliably getting yourself killed. Blood drain and attack should be separate keys: if I'm approaching a human and press D, chances are I want to drain their blood, NOT hit them with my sword, and there really needs to be a better way to distinguish between them than getting right into the enemy space.
Oh, and on my first try I found the chain in the tutorial level, but now I can't seem to find it anywhere? I don't know what's going on here, but whatever it is seems to be a MAJOR oversight on your part.