Quetzalcoatl

Quetzalcoatl (ケツァルコアトル Ketsarukoatoru), often referred to as Lucoa (ルコア Rukoa), is a former dragon goddess and an old friend of Tohru. She was exiled from her seat of goddess after consuming some cursed liquor, that led her to entering into a scandalous affair.

Appearance
When in her human form, Quetzalcoatl becomes a tall, fair-skinned voluptuous woman with enormous breasts. She has long, wavy blonde hair, taking on a turquoise and green color at the ends. She has heterochromia, where one iris has a different coloration from the other. Her left eye is black on the outside and yellow on the inside, with a green, slit pupil. Her right eye is green on the outside with designs and black on the inside with a yellow, slit pupil.

Like Tohru, she keeps her horns but does not retain her tail or decides to keep it hidden. When she first arrives at Kobayashi's home, she dons a pink cap, a choker and necklace (only in the manga), a black tanktop that exposes her stomach (covers her stomach in the anime), jean shorts, thigh high black stockings, and pink shoes.

In her dragon form, she takes a form of a large 'amphithere' dragon with broad feathered wings and a mask-like skull. She is by far one of the largest dragons.

Personality
Lucoa appears to be laid-back and carefree, and is rarely seen without a smile. She is wise, kind and nurturing, and often has advice for her younger kin.

As a former goddess, she is better tuned to human customs, as seen when she explains to Tohru why Kobayashi was not receptive to Tohru's initial cleaning regimen. Despite this, however, Lucoa seems to severely lack some sense of propriety.

Background
Lucoa is a former goddess, who is later stripped of her godhood after consuming a cursed liquor that a friend had given her, which led to a scandalous affair with her sister. However, she claims to be responsible for the development of civilization despite no longer bearing any title as a deity.

She currently resides in the Magatsuchi household as Shouta's familiar.

Shouta Magatsuchi
Quetzalcoatl lives with Shouta but does not work for her stay. The two of them have a complicated relationship as Shouta sees Quetzalcoatl as a demon rather than a dragon. Quetzalcoatl will often try to get Shouta's attention, often ending up embarrassing him instead.

Tohru
An old friend of hers, Quetzalcoatl has faith in Tohru as she asks her and Kobayashi for help in convincing Shouta that she isn't a demon. She also cares for Tohru and will occasionally visit Kobayashi's place to check up on her.

Kobayashi
Quetzalcoatl and Kobayashi have a good relationship. They'll often talk to each other while Tohru is away and Kobayashi trusts Quetzalcoatl enough to tell her how she truly feels about Tohru.

Trivia

 * Lucoa is based from the Aztec god Quetzalcoatl.
 * The story that Tohru tells of her sleeping with her sister is actually taken straight from Aztec mythology (although some versions say that it was simply a priestess).