Coco

Coco (ココKoko) is a small yet fast, barefooted girl who serves as a messenger, among other things. Her title is Assistant Chief of Staff, putting her only a rank below the wizened Byro in standing

Her face's appearance bears a distinct resemblance to a puppy, with a small black nose and some kind of headwear having large, floppy "ears". The greater significance this has to her actual character is unknown. She wears dark blue leggings and a yellow dress.

At first, Coco seems to be a bright, cheery girl who is dutiful to her king and her country. She eagerly follows Faust's orders and is unable to contain her energy. Later, when she learns that the king's plans would endanger her friends, Coco decides to disobey his orders, putting herself at risk. She wants nothing more than to be happy with the people she cares about.

(Source: fairytail.wikia.com)