Some time ago Sasami was fatally wounded when Kagato commanded Ryoko to lead an attack on Jurai. During this battle a Jurai battle ship crashed into the building in which Sasami was in and Sasami fell into a deep chasm where many trees of Jurai. Sasami was going to die when one of the tree's which was Tsunami sensed that she was dying. Tsunami used some of the life force that she had to save Sasami. When this happened two triangle markings appeared on her forehead.
Tsunami and Sasami are now forever destined together. While Sasami is young they will remain two separate beings but when Sasami gets older she will become Tsunami. Sasami has haunting dreams frequently; these dreams are usually visions that are to come. They are not exactly as she sees them in the dream but it gives her an idea on how or what will cause that event to happen. An example was of her dream that Tokimi would take Tenchi away from her when she would need him.
As you know Sasami has two triangles on her forehead well the triangular marks on Sasami's forehead are considered to be a status symbol on Jurai and that is something that all Jurians want. It represents power and only the most powerful of Jurians have them. Not even Yosho has these markings on his forehead. Some achieve this through the use of make-up, however Sasami's are real, and so are Tenchi's.