It's half slice-of-life, half sci-fi. Despite that, I still don't consider this much of a sci-fi show. The sci-fi part is almost entirely unnecessary and doesn't matter very much, as it's only there to move the plot along. If you're not a fan of sci-fi, then that's fine, because they don't make that part too painfully obvious, instead concentrating on the meat of the show: the slice-of-life portion.
It takes place in modern-day Japan, around the year 2001 or so. The main character is a shy girl named Tsubasa (age unknown, but I'm guessing around eight or nine). At the beginning of the show, we see that she's left Tokyo for Hokkaido, because her father got a job offer that requires her family to move cross-country. She has to leave all her friends behind (since, if anyone knows their geography, Tokyo and Hokkaido are on different islands in Japan), and her shyness makes it hard to make new friends in Hokkaido, where the culture is also slightly different from that of mainland Japan. It starts off getting the character to become familiar with her more rural surroundings, as she lives on a ranch in the countryside, with only a small town nearby. You also learn a few things about her family; her mother, for instance, died while giving birth to her. That plays an increasingly important role as the story progresses.
Before going to bed one night, she sees what appears to be a meteor landing deep into the woods behind her ranch. When she goes out to investigate with her new dog Tenmaru, she finds a crashed UFO. The pilot, an alien (who, despite the hair color and his foriegn speech, roughly resembles a human), lies unconscious next to the wreckage. Almost immediately, a large monster of some sort erupts out of the crashed spaceship. The pilot wakes up, sees the monster, and immediately pushes Tsubasa out of the way, saving her from getting killed. He uses a small circular device to transform himself into another form, and immediately begins attacking the monster. Ultimately, he loses, gets impaled on a spike that juts out from the monster's body, and is thrown out of the way, unconscious. The transforming device falls next to him.
The monster, finished with the pilot, spots Tsubasa instead and tries to attack her. In fright, she evades, spots the spaceship's open door, and jumps in, trying to hide. The monster chases her inside, tries to attack her with a spike, and misses. It breaks open a device hanging on the wall, similar to the one the pilot used to transform. A strange liquid oozes out, comes in contact with Tsubasa, and immediately she is transformed.
Within this transformation device is another intelligence, another living being called a "Ribens". When called upon, it transforms the user into a Figure, a combat form with increased strength and reflexes. It's alive, and has its own mind. Upon activation, this being merges with the user and allows him or her to become a skilled combatant.
After turning into a Figure, Tsubasa hears the voice of the other intelligence in her mind. With her insistence, she helps Tsubasa fight. Unlike the pilot, they end up being successful, destroying the monster. Tsubasa is still curious and frightened that she has a mind residing within her, so the Ribens parts with her. When Tsubasa wakes up, she is back to her normal self... but sitting next to her is a girl. A girl that looks exactly the same as her. This "twin" is the Ribens that helped turn Tsubasa into a Figure, but normally the Ribens is supposed to turn back into the small device after parting with the user. Oddly enough, instead of turning back into a Ribens, she turns into a girl. This girl, who shares all her thoughts and memories with Tsubasa, decides to name herself "Hikaru" (you learn why later), and moves in with her and her family, posing as Tsubasa's "twin sister". As Tsubasa never had a close friend in Hokkaido, the two begin to grow a very tight friendship with each other.
Initially, the plot is confusing, but you soon come to understand that the story isn't about the alien threat that now faces Hokkaido, and gradually the rest of the world. Again, all that sci-fi stuff is just there to give the story a reason (though it is pretty interesting). The story is about Tsubasa and Hikaru, the two so-called "sisters", and how their relationship with each other becomes stronger as time passes. It's also a story about growing up and learning how to live and love. Initially, Tsubasa is shy and secluded, but with the help of Hikaru, she gradually becomes more confident and opens up to the people around her as she adapts to her new life in Hokkaido. It's a lovely, sad, beautiful, touching story.
There are only thirteen episodes, but each and every episode is 45 minutes long, pretty much the length of a short feature film, so it more than makes up for how few episodes there are. Unfortunately because of that, each episode is like 650 MB to download, and altogether the entire series is about 8 GB.
I more than recommend this show to anyone though. It's got enough character development to interest shoujo fans, and enough action to interest shounen fans. Even still, I recommend it for the story more than the action.
