Масакі Кійоне

In the Tenchi OVA continuity, Kiyone Masaki is the mother of Tenchi and Tennyo Masaki. Her parents are Katsuhito and Airi Masaki. Her sister is Minaho Masaki. Kiyone's name isn't mentioned in the first two OVA series, despite her appearing in varios flashbacks. While Tenchi thought of his mother as sweet and gentle, it turned out that she was a practical joker. She also loved making things harder than they actually were, such as climbing a mountain to get at some herbs to help cure a cold while there was a meadow of them right next to the mountain. Kiyone, with help from her mother Airi, created an elaborate story for Katsuhito and Nobuyuki to present to Tenchi about her death. In reality, she died of old age.

How she could die of old age while her parents still live is not explained.