Sasami is Aeka's perpetually cheerful little sister. Blue ponytail hair and pink eyes, Sasami is cute and she knows it. Always very polite, she helps with many chores around the house and makes a mean cup of tea if asked (probably her only flaw is mischievous streak that sometimes gets her and others in trouble). Sasami is Ryo-oh-ki's special perch.
In the OVA Sasami arrives with Aeka and plays a supportive role at the Masaki household. Later she reveals she merged with Tsunami as a child after a terrible accident. In the TV series Sasami is stranded on Earth after Ryo-oh-ki crashes into her ship trying to get a carrot. She meets a ghostly friend, Mirei, on the way back to Jurai.
Sasami is chosen as the champion for Tsunami, the future ruler of the magical world. Tsunami gives her the power to transform into Pretty Sammy and fight for good on earth. All the primary Tenchi Muyo characters make appearances in this spin-off, along with new characters, including Misao, Pixy Misa, Rumiya, Ramiya, Biff Standard (Pretty Sammy also appears in the "Mihoshi Special" and the TV series).
Sasami and Tsunami are specially linked, and Sasami can travel anywhere there is a Jurai tree (OVA Ep. 6). Though it appears Sasami possesses ESP in the series, it is Tsunami who is influencing her through the link.