Achika Masaki (柾木 阿知花, Masaki Achika) is the mother of main protagonist, Tenchi Masaki in the Tenchi Universe continuity. Her father is Katsuhito Masaki, previously known as Yosho, the Prince of the Royal Family of the planet Jurai, and her mother is the late Itsuki Masaki. In the official OVA continuity, Tenchi's mother is Kiyone Masaki, a completely different character.
Tenchi Muyo! in Love
In Tenchi Muyo! in Love, the movie immediately following the conclusion of Tenchi Universe, Achika Masaki is Nobuyuki's classmate, and though not forward enough to say it, the two have a crush on one another. But what she didn't realize is that she was the prime target for the intergalactic criminal, Kain, who seeks revenge on the Juraian Royal Family by traveling back to 1970 to kill her, wanting an end to their bloodline and place in power. Should he succeed, Tenchi would never have been born and cease to exist in the present.
With the aid of Washu, Tenchi and the gang travel back in time to prevent Kain from achieving his goal. In the end, Achika recognized her future son's appearance, and unleashing her great, hidden Juraian power, she engages in battle with Kain herself. Though she's able to save Tenchi and her future husband, the immense amount of energy dispelled shortened Achika's own life. With their fates erased from memory, she and Nobuyuki spend what time they have happy together, until when in 1984 Achika passes away, leaving Tenchi motherless at the age of five. Coincidentally Achika's mother also died when Achika was an adolescent.
Unlike her counterpart in Hiroshi Negishi's continuity, Achika's past is set in the original OVA series, and lacks the presence of time travel or Kain. She showed great potential even as a young woman, able to see spirits and speak to Funaho, her father's Royal Tree. Yosho hoped for her to inherit the sword and mantle of the royal family (as Tenchi later would). But she was in love and yearned to remain a normal girl without the burden the title would bring upon her.
Still, Achika did not wish to disappoint her father, and with this conflict in her heart she took the bonding ritual with Funaho... and failed, being wounded severely. The man she had loved abandoned her while she was on the mend, causing Achika's efforts to have been for nothing and her heart to break. A year later, Achika had recuperated but was far weaker than in her younger days, catching notice and marrying the much older Nobuyuki because of his resemblance to her father (both were Yosho's descendants).
After another year had passed, Achika gave birth to Tenchi, and everything seemed well. However, at five years of age the powers latent in the boy surfaced, and in poor condition and unable to defend herself Achika was fatally hurt by the Lighthawk Wings. On her deathbed, she asks her father to continue training Tenchi, as her place was now with the goddess Tsunami.
Tenchi in Tokyo
She also appears in Tenchi in Tokyo in flashback scenes in Episodes 7, 12, and 17 (In episode 7, somehow in the English version, she was referred to as Tenchi's grandmother, but in the Japanese, she is his mother). In this version, she was still Tenchi's mother and Nobuyuki's wife. Before her death, Achika gave Tenchi his crystal necklace as an heirloom and a memento of her, which would play a crucial role throughout the series. She is shown in both her outfit from Tenchi Muyo in Love and Kiyone's kimono from the OVA series.
An abbreviated version of her tale in Tenchi Muyo in Love! is told in Hitoshi Okuda's seventh No Need for Tenchi! graphic novel, unique to its own canon within the series. Most themes are similar to the film, except Achika does not transform and fight Kain by her lonesome. Instead, she releases all her inner strength in one blast, with she and her son killing the villain together. Peculiarly, while she is not shown in her Juraian state during the actual adaptation she is featured as such on the book's cover.