Okay, these are some sloppily-written summaries of Magic Knights Rayearth...at least, the manga version. I included the endings in my summaries, so.....if you don't want to know the ending, then don't read it. Don't worry, I'll warn you when I'm about to blab out the end.
Hopefully, I'll have some stuff on the OAV series, not just some stupid summary of the manga series, someday. So anyways........
Magic Knights Rayearth (or MKR), consists of six volumes of manga, divided into series one and two. The basic storyline is about the three girls Hikaru, Umi, and Fuu. The first series begins with all three girls going to Tokyo Tower on a field trip (all three go to different schools). Once there, all three of them suddenly see this girl calling out for the "legendary Magic Knights" to come "save her world". The three of them get sucked into the floor and end up falling through the sky in some weird world. This is the magical world of Cephiro, where "the Will determines everything". It turns out that the three of them ARE the "legendary Magic Knights" who were called from their world by Princess Emeraude (that girl they saw all of a sudden in Tokyo Tower), the "pillar" of Cephiro. The whole world is in turmoil at the moment, and the girls learn that everything in that world depends on the heart of Princess Emeraude. As "pillar" of that world, she has to concentrate on protecting that world, and doesn't have the freedom to love anything else. The Magic Knights meet some residents of Cephiro, like Mokona (this cute little rabbit-type creature that is perpetually happy and always making these "Bu-bu! bu-bu!!" sounds), Clef, Ferio, and Presea...but I'll do characters later!! Anyways, the knights think it's their duty to save Princess Emeraude, who is supposedly being held captive by some evil priest called Zagato. To rescue the princess and save the world, however, the girls first have to go through tests to call forth the legendary mashin. To me, the mashin look like these humungo robot things...but anyway, each of the three girls has certain powers, like Hikaru's is fire, Umi's is water, and Fuu's is wind (typical). I think the story is really cool in that at the end (here comes the ending, if you don't want to read it you better scroll down to part two now), the knights kill Zagato only to find out that the princess hadn't called them into Cephiro to kill Zagato--she had wanted them to kill HER. She and Zagato had fallen in love and the world was in turmoil because her heart was divided (i don't know how to explain it better!! YOU try it with my sucky reading skills. I read the Chinese-translated versions.). Since a "pillar" can't ever commit suicide, the princess wanted to be killed in order to preserve the peace of Cephiro. But oops, too late...the knights killed Zagato. His last wish (it was really sweet) was for the princess to gain freedom. But when the princess found that Zagato had been killed, she was so anguished that she suddenly, well...grew up (physically. she looked like a seven-year-old before) and decided to kill the knights. The knights had to fight her in self-defense, and were totally getting whipped because they didn't want to hurt the princess. But then they heard the original princess's plea, for them to kill her....see, the grown-up version of the princess was because of her sorrow and anger at Zagato's death. Her old self begged the knights to kill her and end it all. It took a struggle, but they did it. Then they all got zapped back to Tokyo Tower, and appeared there hugging each other and crying because of such a sad and stupid ending to it all. That's the end of the first series.
PART TWO: The second series starts with all three girls in their own homes, all looking really sad and droopy. They meet at Tokyo Tower again, and all of them are really downcast because of what happened with the princess and Zagato. But all of a sudden, they fall through the floor again, just like last time. They end up in Cephiro again, to find the world in turmoil again because there's no "pillar". Three other countries, or rather, three other groups of people, are trying to get into Cephiro by building pathways, the leaders hoping to become the next "pillar" of Cephiro. There's Eagle Vision from the country of Autozam, which is one of those technological countries where people convert their willpower into other stuff in order to have all kinds of high-tech machinery and stuff like that. Eagle wants to become Cephiro's "pillar" because the atmosphere in Autozam is really messed up. Then there's the two princesses of Chizeta or whatever it's called; they're twins who have these two genie things to protect them. They want to get Cephiro because their own country's land area is way too small. And last of all there's this little girl-spoiled brat princess Asuka or something, from the country of Faren, who wants Cephiro because.....well, she just WANTS it. Anyways, all three of these countries are fighting to get into Cephiro to become the "pillar". The thing is, however, to become the pillar you have to have a heart/will that's stronger than anyone else's. The three knights decide to help fight on Cephiro's side to keep those three countries out. They also meet some interesting new characters like Lantis, who's Zagato's brother and who wants to destroy the stupid pillar system so that nothing like what happened to his bro and the princess will ever happen again. He's like Cephiro's only magical swordsman or something like that......But anyway, after you're chosen as one with a strong enough heart/will, then you have to pass a test to become "pillar".
Okay, here comes the ending, for those of you who don't want it...
It turns out that MOKONA, the little rabbit-type creature (he's SO cute) is the creator of the world (talk about CLAMP's sense of humor), and Eagle and...HIKARU are the only ones with strong enough wills to qualify for "pillar". They are taken back to Tokyo to battle it out, but Hikaru talks to Eagle (while fighting), and stresses the feelings of all the heartbroken people left behind when one becomes "pillar" of Cephiro...you're unable to love anyone. Eagle admits that he wants to become Cephiro's "pillar" because he has a disease, and will die soon. He wants to become "pillar", and then die (go into a deep sleep) and take Cephiro with him so that the past can't be repeated (or something like that). However, Hikaru's speech really moves him and also proves that she has the stronger will, so SHE becomes the next pillar of Cephiro. But when the pillar is chosen, the other person who lost the fight disappears forever. Hikaru doesn't want Eagle to disappear, so she drags him back to Cephiro with her...it's really touching (from my point of view anyway) because she gets all cut up and stuff trying to take him with her, and when he tries to make her stop, she reminds him that he's got to keep on living for all the people that love him. Well...as you can probably guess, they both made it back (with help from Umi and Fuu, who also get kind of messed up trying to meet Hikaru on the path and take her back). The world is restored, and the girls are able to come and go to and from Cephiro as they please.