Fruits Basket

From Yen Press:

After a family tragedy turns her life upside down, plucky high schooler Tohru Honda takes matters into her own hands and moves out into a tent! Unfortunately for her, she pitches her new home on private land belonging to the mysterious Sohma clan, and it isn't long before the owners discover her secret. But, as Tohru quickly finds out when the family offers to take her in, the Sohmas have a secret of their own. When touched by the opposite sex, they turn into the animals of the Chinese Zodiac.

Official Japanese:
Manga Park, Mechacomic, Piccoma

Note: Won the 2001 Kodansha Manga Award in the shoujo manga category and the "Best Manga" award at the 2007 American Anime Awards.