Kiyone Masaki (柾木 清音, Masaki Kiyone) is the mother of Tenchi and Tennyo Masaki in the OVA universe. In the Tenchi Universe continuity, Tenchi's mother is Achika Masaki, and has a completely different background, appearance and personality.
Kiyone was Half-Juraian, half-Airaian. She was born to Katsuhito Masaki, originally named Yosho, the crown prince of the planet Jurai and his wife Airi as well as being the younger sister of Minaho. Even though she still looked youthful, she died peacefully at the age of 248 when Tenchi was a young boy after becoming quite senile with her mischievous jokes becoming more senseless as time progressed. Kiyone married Nobuyuki Masaki, a distant descendant of Yosho. Kiyone is also nearly identical in appearance to her daughter Tennyo.Kiyone was known to be incredibly mischievous and even slightly sadistic, showing her love to Tenchi through many pranks. She even writes an extremely morbidly-humorous script for her father and Nobuyuki to follow when explaining her death to Tenchi. The script was co-written by her mother, whom Kiyone gets her mischievous streak. The script involves telling several stories where Kiyone ends up getting hurt, but not dying due to her Juraian heritage, with the stories being completely unrelated to her actual death. After Tenchi gets mad and storms off, Rea, Tenchi's future step-mother, finds him and explains that Kiyone expressed her love through her pranks and that most likely, the mother he remembers quietly smiling at him was probably just her smiling at a joke at his expense. Tenchi eventually accepts that his mother isn't like he remembered her and that she still loved him despite her jokes. He also acknowledges that the image he created for his mother was merely a mix up of his memories, as Rea became a motherly image to him after Kiyone passed on.
In the manga, which is in a separate continuity, her name is changed to Achika because the character Kiyone Makibi is introduced. Additionally, her personality and death is different than in the series. Kiyone's death wasn't a natural one of old age; she was accidentally killed when Tenchi's incredible power surfaced at a young age and ended up accidentally killing his mother.
Based on the conduct of Tenchi's father and his Jurain relatives at the same time as the arrival of Tennyo, Tennyo may not exist and may in fact be Kiyone.