On a quiet, sunny day, Tenchi Masaki leaves home and begins the walk to school-just a normal action on a normal day. But Tenchi cannot help recalling how his life was more like a crazy carnival not so long ago, and how it all began on that one fateful day.
High above the Earth, the space ship Ryo-Ohki is fleeing from an aggressive pursuer. Both ships are damaged, and their battle soon breaks off as they are forced to crash land on the planet below- in the mountains of Okayama. Watching as the mysterious objects fall to Earth as he walks home from school, teenager Tenchi Masaki decides to investigate, and to his surprise, he finds a half-conscious girl in the wreckage of one of the ships.
A handful of cold water is enough to revive the girl, who introduces herself as Ryoko. Ryoko is quick to add that a vicious space pirate is pursuing her, and that Tenchi must help her out. Tenchi has no idea what to make of this, but when a humanoid mecha appears and starts firing at them, it is clear that there is only one sensible thing to do- run away.
Running through the woods, Tenchi and Ryoko are relentlessly pursued by the space pirate mecha, and eventually find themselves cornered on the edge of a cliff. When Tenchi’s attempts to reason with the pirate fail to stop their adversary’s advance, he is sure they are done for- until, to his surprise, the mechanoid steps on a can, loses its balance and falls over.
As the two make a lucky escape from the hopelessly flailing mecha, Ryoko takes the opportunity to kick it over the cliff before following Tenchi home. Back at home, Tenchi’s father Nobuyuki and grandfather Katsuhito are a little worried to see him home so late- not to mention extremely curious as to what Ryoko is doing with Tenchi.
Ryoko is quick to tell the others her story- explaining how she was attacked by a vicious pirate whilst travelling through outer space. A sceptical Tenchi informs her that no one could swallow that story, only to find that Katsuhito and Nobuyuki have fallen for every word of it. After all, to them it seems a whole lot more plausible than accepting that Tenchi could have picked up such a beautiful girl.
Nobuyuki is quite taken with Ryoko, and offers to let the seemingly meek and innocent girl stay the night with them. Promising to protect her against the return of the space pirate, Nobuyuki and Katsuhito have Tenchi board up all the ground floor windows. Nobuyuki then announces that he will diligently stand guard all night- only to fall asleep on the sofa shortly after Katsuhito leaves.
Upstairs, Ryoko makes herself at home, and starts playing a video game in Tenchi’s room. Unable to focus on his homework thanks to the noise, Tenchi decides to go somewhere quieter, despite Ryoko’s pleas that he not leave her alone. Fortunately, the stand-off is broken by a ring at the doorbell, and Tenchi rushes downstairs to answer the door- only to discover the space pirate mecha standing outside.
Whilst the mechanoid smashes into Tenchi’s home, Tenchi and Ryoko beat a hasty retreat. After running through the house, they find themselves cornered in the upstairs corridor. With no other choices available, the two jump out of the window and make a break for the Masaki shrine.
Tenchi and Ryoko make it all the way up the shrine steps, only to be intercepted at the top when the mechanoid jumps over them. Disturbed by the noise, Katsuhito emerges from his house, and to Tenchi and Ryoko’s relief, he promises to handle the situation. Drawing his wooden sword, Katsuhito launches an attack, striking and disabling the mechanoid. The mecha opens to reveal its pilot- another young woman.
Rather than being a space pirate, the new girl is a Galaxy Police Officer named Mihoshi- the real pirate is none other than Ryoko. After sorting through the bizarre junk that she carries with her, Mihoshi finds a pen that opens out to create a computer screen detailing her and Ryoko’s identities.
Realising that the deception is over, Ryoko drops the ‘sweet and innocent’ act, and begins taunting Mihoshi, daring the GP officer to shoot her. When Ryoko refuses to stand down, Mihoshi does indeed begin firing, only to discover that Ryoko is easily able to create a shield that deflects the shots. As Mihoshi continues to fire wildly, Ryoko decides to retaliate. With bolts of energy crackling between her hands, she surges towards the others, and poor Tenchi is once again forced to flee- this time with Mihoshi.
With Ryoko on their heels, Tenchi and Mihoshi run back down the steps and into the house, only to end up in the same dead end on the upstairs corridor that Tenchi and Ryoko ran to. Once again, Tenchi jumps out of the window, with Mihoshi following close behind. Unfortunately, Mihoshi does not land very well, and she hurts herself too much to be able to run anymore.
Unwilling to leave Mihoshi behind, Tenchi decides to stand and fight. As Ryoko hovers above, Tenchi grabs a hoe and prepares to face off against her. Despite his fear, Tenchi stands firm, and to his surprise, Ryoko breaks off her attack and descends to the ground, claiming that the whole chase was just a joke- in fact, she is even ready to turn herself in once Mihoshi reads her rights.
Withdrawing a computer-screen, Mihoshi begins reading the appropriate articles for Ryoko’s arrest, but before she can finish it, Ryoko vaporises the computer with an energy blast. Undeterred, Mihoshi tries to continue from memory- only to realise that she cannot remember the correct words, and hence cannot complete the arrest.
As Mihoshi breaks down in tears, Ryoko announces that she plans to stay with the Masakis for while, and to Tenchi’s horror, she keeps to her word. And, as everyone shares a meal together the next morning, Mihoshi asks if she can stay too. Her ship was destroyed when it crash landed, and now she is stuck on Earth just like Ryoko. Naturally, Katsuhito and Nobuyuki are happy to let them stay- their bachelor-filled house could use nothing more than a couple of young girls to brighten the place up.
Later that morning, as Tenchi gets to work fixing the damage caused by Ryoko and Mihoshi, he can’t quite believe that the girls will really be coming to live with them. With two personalities like theirs around, things are certainly going to be different from now on.