The merciless criminal Kain has escaped from sub-space where he has been captured! Kain, who was deprived of his freedom by the Jurai royal family whom teamed up with the GP (galaxy police), has demolished the GP headquarters and attacked the Jurai King. His next target is earth! Around the same time on earth, Tenchi's house has suddenly disappeared. What's even worse is that Tenchi's body is disappearing too! Something must have happened in the past to Tenchi's mother, Achika. So the gang must now leave for a journey to the year 1970 to save her......

Tenchi Muyo! in Love

The story opens with the destruction of the Galaxy Police headquarters. One of the most powerful, but feared and vicious criminal to ever exist has pulled off the impossible and escaped from sub-space, and now he has a thirst for the blood of Jurai. The entity's name is Kain, brought havoc upon his place of capture, and is seen flying off into space, heading for Earth. After a moment, a variety of different scenes of the main cast begin to play, showing them in rolls and places that are rather confusing, making you wonder what exactly is going on. The brief montage fades out into an amateur film of a young, beautiful girl named Achika. Tenchi and the gang are relaxing late one night, watching the old home movies, and everyone is shocked to find out that the girl they have been watching is actually Tenchi's mother.

Things, however, don't stay normal for long. Suddenly, Achika disappears from the film, and Tenchi goes flying through the air before anyone even has a clue as to what's happening. Luckily, one person already has a grip on the situation: Washu. Sensing a disturbance in the balance between time and space, she hurried to the room, and saved Tenchi using a force shield before he "disappeared." Before he disappeared? It seems that something has happened to Tenchi's mother in the past, and Washu proves this by looking at the film footage, on which Achika slowly vanishes, frame by frame. Thus, at that moment in relative time, whatever happened to Achika caused Tenchi to never be born, and he was almost erased from existence. Washu has a slight idea of when the disturbance in time and space happens, but beyond that, little else is know as to what it is that has happened, or why. A decision is made, and only one solution is seen: travel back into the past, and make sure nothing happens to Achika.

Tenchi, Ryoko, Aeka, Sasami, Mihoshi, Kiyone, and Ryo-oh-Ki all arrive in 1970, and position themselves in different places near Achika to watch over here; Ryoko and Aeka are students, Kiyone a school janitor, Mihoshi a teacher (!), and Sasami and Ryo-oh-Ki watching after Tenchi, should he start to break into non-existance again. Meanwhile, Washu is back in the present, trying to figure out exactly what it is that causes Achika to be lost, and continues to update the group as to what she has found. Finally, the pieces of the puzzle begin to fit together. Kain, the class-4 criminal, was captured by the house of Jurai. Finally free, he seeks revenge against the family of Jurai, and has chosen Achika as his current target. Time slowly runs out until the time in which Achika is set to dissapear, and a fierce battle erupts between Tenchi, Noboyuki (Tenchi's father), Achika, and the criminal Kain.

After a few false alarms, Washu pinpoints the exact time of the attack: when the school goes to Tokyo Tower for a field trip. So the crew set up a trap for Kain.

At the field trip, Kain makes his move. Tenchi rushes in to save his mother(who's a high-schooler at the time). Kain senses a Jurain presence but can not distinguish whether it radiates from Tenchi or Achika. After a struggle, Kain is sucked into the trap, but not before he grabs Nobuyuki(Tenchi's father) and Achika. Frustrated, Tenchi, Ayeka and Ryoko find a way to get into the trap as well. Tenchi, Ayeka and Ryoko try fighting Kain but it seems useless. When Achika wakes up and finds a beat-up Nobuyuki, her Jurain powers manifest themselves. She transforms into a Jurain kimono, grabs Tenchi's sword, and slays Kain.

In the end, Kain is no more and the gang is pulled out of there. With Achika safe, Tenchi is able to be born. The movie ends with a sentimental scene where Achika tells Ayeka and Ryoko to take care of Tenchi. Where is Achika in the TV series? You just have to see the movie and find out what happens to her.There's a lot more to the movie than just that summary. There are a lot of drama elements as well, such as how Nobuyuki and Achika came together, why Tenchi is named Tenchi......just many things about Achika you ever want to know about.