Syaoran
Syaoran is strong and kind character, mostly reffered to as "boy". Syaoran, although cheerful and knightly, is carrying the wounds from his past in his heart. Adopted by archaeologist, Fujitaka, he accidentally came into the country of Clow. Here he met daughter of king, Sakura. Currently he is traveling together with Fai, Kurogane and Sakura, in order to regain Sakura's lost memories, in form of feathers. But to do so, he had to give up his most precious thing - his relationship with her. Thus, even if she regains all her memories, she won't remember him.
One of Syaoran's eyes is blind and seems to be connected to misterious events surrounding him and his past.
Manga Spoilers
It is latter revealed he is actually a clone of the original Syaoran. He was created by Fei Wong Reed to collect and scatter Sakura's feathers. Original Syaoran ,before being captured by Fei Wong Reed, placed half of his heart within the clone.
Sakura
[ Information from Wikipedia - Spoilers may follow ]
At the start of the series in both manga and anime, Sakura is the princess of the Kingdom of Clow who has feelings for Syaoran, her childhood friend.
When she is about to confess her feelings, a mysterious force causes her own dormant magical powers to manifest in the form of feathered wings. When her feathers are scattered across time and space, Syaoran vows to recover all of them because each feather represents a memory Sakura has had since birth and are connected to her heart; without the feathers, she will die.
Fei-Wong Reed (the mysterious villain in the series) reflects on the ability of people like the High Priest Yukito, Princess Tomoyo of Nihon, and Yūko to cross dimensions and comments that the power concealed within Sakura and the ruins in Clow Country surpasses them all.
In order to cross dimensions, Sakura must pay Yūko the thing most important to her and she pays Yūko in an indirect way but her price is pretty much the same as Syaoran - her memories of him. When she awakes in the Hanshin Republic the first person she sees is Syaoran, but she does not remember anything about him, asking "Who are you?"
At times, such as in Ōuto, Sakura comes extremely close to remembering Syaoran but it is quickly erased once more from her memory. Syaoran, having known this would happen previously, will never tell her anything about their previous relationship. At most, all Sakura knows about Syaoran is what she has relearned from the adventures together with Mokona, Fai, and Kurogane, although she knows she knew him previously and he was very important to her. It is also clear that she is falling in love with him once more.
Sakura possesses unnaturally good luck; both Chun Hyang and Yūko call her "a favored daughter of the gods". This is what allowed her to travel dimensions safely until Yūko asks for her good luck as a price. According to Yukito and Syaoran, Sakura also has the ability to "hear" the voices of those who cannot be heard, such as spirits of nature, and to see ghosts. Such as the time in the Country of Jade, she can see Princess Emeraude while others couldn't. She can also see the future in visions, though this ability is unreliable and nothing she has control over.
Sakura's personality is passive and weary, exhausted from her loss of memories. However as the series goes on, she becomes more stronger and independent. Syaoran states, even though she's lost most of her memories, she'll never change. She helps the group whenever she can, whether it's washing dishes or saving their lives.
However later in the manga, her personality undergoes a change after the clone Syaoran leaves her. As she voices to Fai, no matter how identical the two Syaorans may be, the real Syaoran is still not the one she knows. Subsequent chapters show Sakura with a much darker personality, accompanied with gothic clothing.
In the Infinity Arc, the group spent a few months fighting in a tournament, supposedly wanting to use the prize money to restore a world the clone Syaoran destroyed. However, the truth is that she was after the real prize - a robot (who is identical to Freya from Chobits) who can let one person and one person alone travel across dimensions.
It is later revealed that Fai is under a curse that forces him to kill if he ever meets a person that is stronger than him. And in volume one, you can see that Yūko was not hit by the rain, nor did she touch any of the people directly; this was because she was in another dimension to prevent Fai's curse from being activated. But when Sakura receives two feathers in the Infinity Arc, she was made stronger than Fai's halved magic and so he stabbed her, seemingly possessed. Sakura had a vision that after killing her, he would go insane and kill everyone else, eventually committing suicide, but she used the robot to transport her soul to a dream world, thus saving herself and stopping Fai from going insane.
Later, it's revealed that she was not the original target of the curse, as the real Syaoran was. This is explained further in her appearance in xxxHolic; she changed the future so that Syaoran would not be killed. As she explains to Watanuki (Xxxholic chapter 140), her coldness to the real Syaoran was because she was trying to follow the dream as close as possible up to that near fatal event. It's later learned that Sakura can still be saved. The two places where her body and her soul went contains two feathers. Her soul went to the world of dreams, where it will be aided by the other Syaoran. So the real Syaoran, Fai, Mokona and Kurogane went to Celes Country to rescue the body of Sakura, as Yūko told them it's the body they should rescue first, then the soul.
Fai D. Flourite
Fai’s introduction is in chapter two of the manga, in which he is shown sealing away King Ashura of Celes country at the bottom of a pool. He transforms his creation Chii [ originally from Chobits ] into a net-like shield, instructing her to alert him if King Ashura should awake. He then uses his magic to transport himself through dimensions, to the shop of the Space-Time Witch, Yūko Ichihara.
Out of his travel companions, Fai’s motives for joining the group are the least clear. He was the only one to arrive at Yuuko's shop purposefully, by use of his own means. His wish was to never return to Celes country, but as the price for this would have been too great, he travels worlds with the group instead. He fears King Ashura’s awakening, believing King Ashura will chase him through different worlds. The basis for this fear is as yet unknown. (Source: Wikipedia)
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Manga Spoilers
Chapter 155 of the manga gives a brief history of his past. As revealed in the chapter, "Fai" was born with a twin named Yuui. In Valeria Country, the birth of the second prince's son was highly anticipated. However, since twins were born, they were considered as a bad omen in the country. Shortly after their birth, the first prince died, and their mother committed suicide out of guilt, blaming herself for giving birth to them. Along with other misfortunes, the country's crops did not grow, and the water became tainted.
In addition, the twins, when combined, seem to bear powerful magic that rivaled that of the current king; when they grow up, they would possess power surpassing that of the king. Believing that the country will not prosper unless the twins were unhappy, the king gave them a choice: have one kill the other or have both locked up separately in a place where magic is ineffective. Since both refused to kill the other, they were thrown into a valley, where magic is useless, and were imprisoned inside a tower; Fai was imprisoned atop the tower, and Yuui was to confined at the base of the tower. This valley was a place for "sinners", the twins were to stay in the valley "until the world's destruction."
However, despite the twins' misfortune, the number of dead "sinners" dumped into the base of the tower began to grow. While "Fai" looked on from above, Yuui tried endlessly to climb up the prison so both Fai and himself could escape, even using dead bodies as a ladder, but the wall proved itself to be too high for him to reach. As time passed by, even innocent people of Valeria were killed and thrown away by the elder king of Valeria, who went mad. Yuui witnesses the King's suicide before his very eyes, as he was told once more that his and Fai's very presence is a curse. This causes Yuui to go mad also, wondering if it is a sin to live.
Later, Fei Wong Reed appeared through a hole from another world, and offered one of the twins a chance to escape- but only one twin. After Fai chooses Yuui to escape, not wanting his brother to suffer any longer, Fai fell from the top of the tower and died. In order to find a way to bring his brother back, Yuui allowed Fei to bestow two curses upon him; one curse was erased from his mind, though Fei was positive he would still fulfill it. Later, true to Fei's prediction, Ashura came to Celes from another world in order to retrieve Yuui. It appears that the protagonist "Fai" is actually Yuui, who has taken on his brother's name and memories.
Cyurrently Yuui/Fai has given all the magic power he has left to Yuuko in exchange for a new arm for Kurogane
Kurogane
Kurogane is serious and extremely perceptive, being able to quickly discern Syaoran's fighting ability (along with Syaoran's blind right eye) as well as Fai D. Flourite's true nature and fighting capabilities. While he seems rather irreverent, he is also very loyal. He is likely the most experienced fighter in the group and wiser than he appears. He becomes Syaoran's sword fighting teacher, presenting the boy with the same philosophy he believes in: a sword is used to cut only when needed and not used to cut anything if it is not necessary. While serious, Kurogane is very easily irked by others, especially by Mokona Modoki and Fai, who keep calling him ridiculously cutesy nicknames such as "Kuro-puu", "Kuro-wan-wan" or "Kuro-rin". However abrasive and ruthless Kurogane may seem, he has a compassionate nature and a desire to protect. An example of this would be how Kurogane continually questions Fai on his actions and character, and lets the wizard know that he should stop hanging onto his past and embrace the future with his new companions. Or, Kurogane's own statement that "If someone wants to take away the ones I want to protect, I'll kill them too".
His compassion and protective nature is especially clear when his actions early in the series are compared to his actions later on. He had straight out told Syaoran in their first world, the Hanshin Republic, that the quest has nothing at all to do with him. In the next world they visit (Koryo Country) however, Kurogane offers his services to help raid the castle of an evil lord, and stays behind in battle to let Syaoran go on ahead. Eventually, he risks a loss in strength to avenge his comrades' "death" (they were of course still alive) by defeating their killer in battle. It is noted that after he finds out Fai and Syaoran are still alive, he lost his passion for the battle.
He obtained a new sword in Ōto called the Souhi (Blue Ice) and taught Syaoran the skills of sword fighting and sensing attacks from the left. Thanks to Fai, Kurogane can now summon his sword from his right hand in a similar way to Syaoran in case Mokona is not there to give him his sword.
Manga Spoilers
At the beginning of the story, Kurogane told Syaoran that he would not help in finding Sakura's feathers, since it was not related to him. However, he ended up aiding Syaoran and the others anyway, teaching Syaoran how to fight and use a sword as well.
In the Tokyo arc, Kurogane was involved in a short fight with Kamui. Later, he wished to Yuuko to save Fai's life, after Fai's eye was ripped out by the clone Syaoran. Through an arrangement by Yuuko, Kurogane and Kamui mixed their blood and forced Fai to drink it. Fai thus became a vampire and survived. Since it was not Fai's wish to live but Kurogane's, Fai can only take blood from Kurogane. Fai painfully refrained from calling Kurogane nicknames from then on, in an effort to distance himself from Kurogane.
Kurogane noticed that Fai and Sakura were up to something in the Infinity world, but did not say anything. After Sakura left, however, he finally spoke up, refusing to let Fai give up his eyesight to go to Celes. Kurogane told Yuuko they would all pay a fourth of the price to go save Sakura's body from Celes.
In the latter parts of Volume 20, Ashura used his magic to show Syaoran, Kurogane, and Mokona visions of Fai's tragic past. This caused an angry and betrayed Kurogane to unsheathe his sword and attack Ashura and Fai. He and Fai fought fierce battle that devastated the room around them. In the mayhem, Kurogane destroyed the body of Fai's twin and managed to overpower Fai in that moment of weakness, saying to the overpowered Fai something along the lines of "I thought I already told you I don't have anything to do with your past". Kurogane then turned on Ashura, demanding to know why he'd shown them Fai's memories. The king responded by saying that he only wanted Fai to "grant his wish" and kill him. Ashura then launched vicious spells against Fai, Kurogane, Syaoran, Mokona, and a defenseless Sakura's body in order to force Fai's hand. In the chaos that followed, one of the massive ice stagamites that he conjured pierced Kurogane through his lower right side.
Korogane is then apparently spared the damage due to the protective spell that placed upon him before leaving Japan by Tomoyo. He then stabs King Ashura, and after the King's death the group is seen possibly leaving for the next world.
Fai's second curse caused him to suck up the world of Ceres; Fai tries to transport Kurogane and the others out of the small sphere that Ceres has become, but he doesn't have enough magic to do so. He only succeeds in transporting Syaoran, Sakura, and Mokona. Then Mokona's earring (a magical tool made by Yuuko) was able to drill a hole into the sphere, but only one person could pass through. When Fai told Kurogane to leave him, Kurogane cut off his left arm and left it and Souhi as a sacrifice and rescued Fai.
In chapter 167, Kurogane wakes up and finds himself back in his country, with Princess Tomoyo by his bed. Tomoyo welcomes Kurogane home and asks him if he has found out the true meaning of strength, to which he replies that he doesn't know. However, he explains to Tomoyo that he doesn't regret giving up his arm to take Fai with him, and tells her that he knows that some things can't be protected only by (physical) strength. This surprises Tomoyo, but she acknowledges that Kurogane has definitely realized the true meaning of strength. She then lets Fai into Kurogane's room. Kurogane seems genuinely pleased to see Fai, while Fai doesn't express much emotion, until suddenly - he punches Kurogane. Kurogane doesn't quite react to this, far too startled. Fai then smiles at him, saying "This is payback, Kuro-sama." The smile seems like the real thing, and Fai has gone back to using suffixes on Kurogane's name. Kurogane grins back, promising to beat Fai up for that.
In chapter 169, Kurogane is approached by Fuuma who has come to Nihon Country with an artificial arm from Piffle Country, however Kurogane refuses the arm by saying that he "will not pay anything to that witch for it." Fai replies by saying that he had agreed to pay the price while he slept, and gives up the last of his magic. In the second to last page of 169, Kurogane is seen with the arm attached, but claims that it "feels weird."
Real Syaoran
Mysterious person kept asleep in a liquid chamber at Fei Wong Reed's palace, with his left eye covered by a piece of cloth, his hands and arms by binding spells and wearing clothes marking Fei Wong Reed's bat symbol.
Manga Spoilers:
In fact, this Syaoran is the original while the Syaoran at Sakura's side is only a clone that Fei Wong Reed created. This Syaoran is of Clow Reed's bloodline and can thus use magic. He gave his eye and with- it half of his heart to his clone to stop Fei Wong's plan temporarily. He was depicted as a villain (it was believed that he was controlling the clone's actions, while it was only the clone's true nature showing) until it was discovered that the protagonist Syaoran is his clone. This Syaoran is able to summon a sword which looks exactly like the one used by Syaoran Li from Cardcaptor Sakura and also uses the same spells.
