Yuuki Miaka and Hongo Yui have been best friends since Kindergarten. They are very close, but over the years, they have began to grow more and more competitive. They are both competing to be excepted into the same high school, and must fight to keep up their grades to get in.
One day, the two girls go to the library to study for the upcoming entrance exam. Miaka, who never seems to stop eating, stops at the candy machine to get a quick snack before they begin. The clumsy girl she tends to be, Miaka drops her coin and watches helplessly as it seems to fall to the ground in slow motion. When she looks up, she sees a bright, shimmering bird with sparkling light pouring from its wings. It soon turns the corner and disapears.
Like fire! Miaka follows where she thinks the bird has gone. It leads her to a room that isn't open to the public. A room with old books that no one has even touched in years. Yui walks in (although I don't know how she finds Miaka. She must have followed her), and asks her what she's doing in that room. Suddenly, a book falls to the ground, and opens to the first page. Yui and Miaka pick up the book together, each holding one end of the cover. They read outloud. It says:
"This is the story of a girl who gathered the Seven Seishi of Suzaku, and acquired the power to make every wish come true. The story itself is an incantation. Whoever finishes the book shall receive this power. As soon as the page is turned, the story will become the truth and begin..." They turn the page, and are sucked into a different world. An ancient world that is home to many legends. The two girls look around, shocked. They realize they have been stolen from the place they knew, and look upon their new surroundings; what appears to be a desert.Miaka and Yui wander around, and soon meet two strangers. The strangers make it very clear that they intend to take the two girls to town and sell them as slaves. Horrified, Miaka and Yui try to run away, but are caught. Miaka bravely defends, telling Yui to run. Yui can't leave her best friend.
As if out of nowhere, a mysterious figure starts to fight the two fiends, defeating them with skilled martial art techniques. Yui and Miaka are stunned as they see a handsome young man with a glowing red symbol on his forehead. The symbol means "Ogre."
The handsome stranger makes it quite clear that he only saved them because he thought he might get paid. The stranger, who introduces himself as Tamahome, states, "Money makes the world go 'round!" He soon starts to leave, and Yui feels something odd happening to her...
Yui is disappearing!! She finds herself back in the library, and begins to read the book. As she reads, Miaka is in there! She is following Miaka's words and actions as they are happening in the mysterious world.
When Miaka notices that Yui is missing, she thinks Tamahome has kidnapped her, and she follows him to the town. When she reaches there, she finds that they are in Konan Country. Miaka desperately searches for Tamahome, hoping she can find her Yui-chan and return home to safety.
To make a long, long story even shorter, Tamahome and Maika are brought to the Emperor's dungeon, because Miaka started to disappear, and was surrounded by a red light. The Emperor suspects that she is Suzako no Miko, a girl who is supposed to appear from another world to gather the Suzako Seishi and summon the god Suzako. As they suspect, she is. Tamahome is one of the Suzako Seishi, along with the Emperor, the young (and handsome!) Hotohori.
(Cutting the story even more shorter) Yui realizes that everything that happens to Miaka happens to her as well. When she falls into a fountain, Yui's clothing are soaked. When Miaka's leg is injured, Yui sees blood on her school uniform. When Miaka has a fever, Yui feels flushed. One things connects them. Something that exists in both worlds; their uniforms
Miaka must return home before she becomes more ill. She is so homesick, she may not even live. So, she concentrates hard on Yui, and she is brought back to the library. This is when Miaka discovers that Yui has traded places with her. She then realizes that a few days or even a month in the mysterios world is only a short time in her world. Only a couple of hours.
Yui arrives in the other world, in the bad part of town. It's nearly deserted. She walks around, looking for Miaka, and two thugs notice her and think she's pretty. She runs for her life, but they catch her and attack her. Yui is saved by Nakago, a leader of the Kotou country army, but she has already passed out. When she awakens and realizes what has happened, she tries to kill herself by slashing her left wrist, because she believes she has been raped. (Nakago doesn't correct her.)
Yui learns that she is to be Seiryuu no Miko, Miaka's enemy. She doesn't want to be, but Nakago convinces her to think about it. Finally, Miaka comes back to the ancient world, and goes to Kotou country to find Yui. She brings Tamahome with her. Yui is delighted to see Miaka, but even more delighted to see Tamahome. She becomes infatuated with him. She leaves Tamahome and Miaka and retrieves the scroll that was stolen from Miaka by Nakago, who took it from her bag earlier. Yui gets the scroll and hurries back to them, happy that she can go to Konan country and be with Tamahome. When she looks into the room, Tamahome is telling Miaka that he loves her. He kisses her, and Miaka tells him that she came back for him.
Yui is shocked. Her best friend returned to the world not for her, but for Tamahome. Her dreams of happiness are suddenly shattered. She feels betrayed, and now wants Tamahome even more. She loves him because she doesn't want Miaka to have him. Cheerfully, Yui enters the room and says she'll go back to Konan with them. She leads them right into a trap, in which they escape. Tamahome offers to take her with them, but Nakago won't allow it. Yui now hates Miaka even more for leaving her. She didn't come back to save her Yui-chan. She came back for Tamahome, and no one else.
Yui has decided to become Seiryuu no Miko. She and Miaka are now officially enemies, and Yui vows revenge on Miaka a thousand times over.
Please note that I wrote this from my knowledge of the series, and this summary is in my own words. Please do not use this summary without written permission from me.
