According to this chart, Nanako is supposed to be the Horse. But it's obvious she's not dressed as a horse at all.

lol kagami supposed to be rabbit

Nanako is not an alpaca (as the current tag would suggest).

She is a horse, and not just any horse, but a a grass mud horse. Grass mud horses are said to be lively, intelligent and tenacious. They eat grass and fight bravely against the censorship imposed by the Chinese government over the content of the internet.

How do you figure that?

As a native Chinese, I totally agree with what PowerToole talks about.
That is a Grass Mud Horse (Sounds familar with Fxxk your mother in Chinese mandarin), in order to express our indignation against the corrupted Chinese govn't. (I wish there's no Chinese cyber police browsing Danbooru otherwise I will be arrested. T_T)

mutsurini said:
How do you figure that?

How did I figure she is one of the legendary grass mud horses?
Well, first of all, she doesn't look like a regular horse, which is what the Chinese zodiac calls for. Then I remembered that the grass mud horse look remarkably similar to the alpaca. I'm Chilean, so I know South American camelids. In fact I used to ride a guanaco to school every day.

And now lookingfrank, a native Chinese, agrees with me. Even the tag "grass mud horse" has been added, and it wasn't there when I posted my first comment. I checked.

Keep on fighting for freedom, confusing-looking horse!