Sasami is the Younger sister to Ayeka, and a member of the Jurai Royal family. During Ryoko's attack on the planet Jurai Sasami suffered a fatal accident, it was then that Tsunami, the most powerful of Jurai's Tree-ships joined with Sasami saving her life. They are one and the same being now. This causes Sasami to have prophetic dreams. When Sasami or Tsunami is standing near a pond one sees the reflection of the other in the water (although aparently this does not happen when she looks into a mirror). Tsunami appears as Sasami aged several years, this caused Ryoko and Ayeka a lot of stress as Tsunami is (apparently) better looking then either of them, and also (of course) in love with Tenchi