Origin: Mentioned in the Kojiki, Japan's oldest book, Yamata no Orochi was a very big Japanese dragon with eight heads.
Description: Yamata no Orochi had an eight-forked head and an eight-forked tail; its eyes were red, like the winter-cherry; and on its back firs and cypresses were growing. As it crawled it extended over a space of eight hills and eight valleys.
Story: The warrior Susanoo slayed the dragon by getting it drunk on sake and then cutting off all its heads. In doing so, he saved the princess Kushi'inada, who otherwise would have been sacrificed. She was the last of eight daughters, all the rest of which had already been eaten by Yamata no Orochi.
Susanoo (alternately spelled Susano'o, Susa-no-O, or Susanowo) took a sword which was found in one of the dragon's tails, called Kusanagi-no-Tsurugi, which eventually was passed down from generation to generation, becoming one of the three Imperial Regalia of Japan.