The film takes place after the conclusion of Tenchi Universe, and so varies from the original OVAs at several points. Most noticeable of these is the inclusion of Achika as Tenchi's mother instead of Kiyone Masaki.
The movie was followed by Tenchi Muyō! In Love 2 - Haruka naru omoi (Tenchi Forever! in the US), released in 1999.
After being defeated by the Jurai Emperor and the Galaxy Police centuries ago, the monstrously powerful Super A-1 class criminal Kain was imprisoned in the subspace room of the GP's headquarters, never to be released.
In the present (established to be 1996, the year of the film's release), Kain escapes his bonds, destroys the GP space station, and travels back in time to take his revenge on Jurai's royal family. The Galaxy Police only has time to send a short warning, which Mihoshi and Kiyone intercept.
The Masaki house, the shrine, and Tenchi himself all begin to fade out of existence. Washu theorizes that someone is tampering with the established timeline, and uses a shield to keep Tenchi from vanishing. The shield is only a temporary solution, so Washu sends the rest of the group back to 1970 to prevent Kain from killing Tenchi's mother Achika.
Tenchi's friends assume roles at Tenchi's father Nobuyuki and Achika's high school, while Tenchi himself stays hidden to prevent causing a paradox. Tenchi and his friends must also deal with a rogue GP operative bent on seizing glory by killing Kain.
After determining the exact time that Kain strikes in 1970, the group tries to defend Achika, only to see the villain escape into subspace with her and Nobuyuki. Tenchi, Ayeka and Ryoko follow and challenge Kain, but even with their powers boosted by Washu they are no match for him.
Washu sends a powerful "dimensional cannon" from the present, and Kiyone mans the weapon to destroy Kain. Tenchi is wounded, and Achika unlocks her latent Jurai powers to fuel his sword and deal a crippling blow to Kain. The group barely escapes in time before the dimensional cannon is fired into their pocket of subspace, finally destroying Kain.
Before her memory is wiped along with Nobuyuki's, Achika asks Ryoko and Ayeka to take care of Tenchi, since she will not be there for him in their present.
The end theme song is Alchemy of Love, written by Franke and performed by Nina Hagen, with Rick Jude on backing vocals.
There is also an Achika version of the song, with new Japanese lyrics, and is performed by Megumi Hayashibara (Achika's Japanese voice actress). The Achika version is available on a single mini-CD (Pioneer PIDA-1033) and on the Japanese LaserDisc version of the movie, as a music video, which also features the original English version.
Overseas, various companies distributed subs and dubs of this film, including Pioneer Entertainment in the USA. In America, it was initially released on home video by Pioneer through Live Entertainment before Pioneer released it independently on DVD in 2003.
- Tenchi Muyo Movie 1: Tenchi in Love (anime) at Anime News Network's Encyclopedia