I do agree with the comment above. The romance tag would be more informative.
Other than that, this is a work of genius. The simplicity of the art gives you so little information, and the fact that you barely know anything about the world or about how any of the zombies came into being- along with, of course, the girls crazy actions- it doesnt feel like there are many stopping points at all in the story. To me, it feels like a dream of a manga. Incredible.