Kingdom Hearts: Birth By Sleep

There are many mysteries surrounding the keyblade. Legend says that it chooses its master, a person with a strong heart. Legend also speaks of two different stories. One says the wielder of the key saved the world, while another that he wrought chaos and ruin upon it.
What events led to putting the worlds in the chaos and threat they are in at the moment? The worlds were already in turmoil before Sora received the keyblade, and Mickey seemed to be a head of the game?
This led to Square answering some of the unanswered questions, with the release of Birth By Sleep in 2010 for the PSP.

Characters:
The three main characters are Terra, Aqua, and Ventus—called Ven for short—a trio of close friends and apprentice Keyblade-wielders under Master Eraqus who aspire to become Masters themselves. Another Keyblade Master, Xehanort, and his mysterious apprentice, Vanitas, serve as the game's antagonists. Other characters from the previous games return, such as Sora, Riku, and Kairi, though they are younger than their original incarnations and given less prominent roles. A number of characters who later come to form Organization XIII also appear, particularly the first five apprentices of Ansem the Wise (Braig, Dilan, Even, Aeleus, and Ienzo) as well as Lea and Isa, who were previously unaffiliated with the former five. As with the Heartless in Kingdom Hearts and the Nobodies in Kingdom Hearts II, Birth by Sleep introduces a new type of enemy: the Unversed, fledgling emotions that are "not well-versed in their own existences" and feed on negativity.
As with the other games in the series, Birth by Sleep features an extensive cast of Disney characters. The most prominent of these characters is King Mickey, who serves as a student under the sorcerer Yen Sid at this point in the series chronology. Donald Duck and Goofy, who served the main protagonist Sora in most other games, appear in smaller roles. Most other Disney characters remain in their respective worlds regardless of their overall importance to the story in previous installments, such as Maleficent and Pete, who served as major antagonists between Kingdom Hearts and Kingdom Hearts II, and a number of the Princesses of Heart. Some characters (such as Experiment 626, Prince Phillip, and King Mickey) occasionally fight alongside the player characters in battles as partners similar to the other games, providing assistance and performing combos to help the player proceed. However, they do not follow the player around constantly like Donald and Goofy in the other games. Unlike the other major installments, which also featured casts of various characters throughout the Final Fantasy series, Birth by Sleep only features two of these characters: Zack from Final Fantasy VII, and Moogles, from several of the Final Fantasy games. As Birth by Sleep is a prequel of the first Kingdom Hearts title, the staff decided to add Zack to the title as he is protagonist from the Final Fantasy prequel, Crisis Core: Final Fantasy VII.

Plot
The story begins in the Land of Departure, where Terra and Aqua take an exam to achieve the Mark of Mastery, allowing them to become Keyblade Masters. However, only Aqua passes while Terra fails due to the abundant darkness in his heart. Shortly after the test, Master Xehanort disappears, and a horde of mysterious creatures called the Unversed begin to appear throughout the worlds. Master Eraqus learns from Yen Sid that the Princesses of Heart are in danger from the Unversed, and orders Terra and Aqua to destroy the Unversed and find Xehanort. Ventus is driven into following Terra against Eraqus's wishes by Vanitas, Xehanort's apprentice, and Aqua is sent to watch over Terra and bring Ventus back to the Land of Departure.
Upon arriving in several worlds, Terra, Aqua, and Ventus encounter various Disney characters, fighting off many Unversed along the way. One of the characters they meet is Mickey Mouse, the apprentice of Yen Sid, who is also on a mission to destroy the Unversed, albeit against Yen Sid's wishes. Terra ends up attracting the attention of several Disney villains, who offer him the whereabouts of Xehanort in exchange for assistance in their own agendas. Upon finding Xehanort, Terra is instructed by him to destroy Vanitas, who is revealed to be the source of the Unversed, created from the darkness of Ventus's heart. The three briefly reunite at Radiant Garden where Aqua and Ventus confront Terra about his actions, but he leaves to continue Xehanort's mission.
Ventus comes across Xehanort, who reveals his intentions to use Ventus's heart and fuse it with the heart of his other half, Vanitas, to create a final Keyblade known as the χ-blade. He sends him to the Land of Departure to confront Eraqus, saying he knows the truth about him. Eraqus tries to kill Ven to prevent Xehanort's plans from succeeding, but Terra, who has also been sent to the Land of Departure by Xehanort, faces Eraqus to protect Ven. Upon his defeat, Eraqus is vanquished by Xehanort, who covers the Land of Departure in darkness and tells Terra to go to a world known as the Keyblade Graveyard. Ven is similarly instructed to do the same by Vanitas, as is Aqua by Yen Sid after he informs her of Eraqus's death.
Terra, Aqua, and Ventus gather at the Keyblade Graveyard, where Xehanort appears with Vanitas and reveals his plan to use the χ-blade to unlock Kingdom Hearts and unleash the secrets of the Keyblade War onto the various worlds. Terra's heart is swallowed by darkness in the ensuing battle, allowing Xehanort to take over his body, but his will remains within his discarded suit of armor, which comes to life and defeats Xehanort. Meanwhile, Ventus is forced to fuse with Vanitas to create the χ-blade and battles Aqua alongside Mickey while he engages Vanitas in a metaphysical battle within his mind. Aqua shatters the χ-blade as Ventus destroys Vanitas from within, though Ventus loses his heart and falls into a deep sleep as a result.
Upon learning that Ventus will not awaken, Aqua brings his body to the ruins of Land of Departure, where she seals the world's keyhole and transforms it into Castle Oblivion to ensure Ventus will not be disturbed. Aqua then goes to Radiant Garden where she fights Xehanort, who still possesses Terra's body. The battle rages until Terra's presence manifests, resulting in Xehanort unlocking his own heart and falling into the Realm of Darkness. Aqua saves Terra but becomes trapped in the Realm of Darkness in the process. Xehanort, who has lost his memories, is discovered and taken in by Ansem the Wise, ruler of Radiant Garden, as his apprentice. Ven's heart then reconnects to the young Sora's and is able to rest within his heart.
In the game's secret ending, which takes place after the events of Kingdom Hearts II, Aqua comes across Ansem the Wise in the Realm of Darkness and learns from him about Sora, who has the power to save those connected to his heart, including Terra, Ventus, and Aqua herself. Sora, having learned of their fates from King Mickey, decides to undertake another quest in order to find and save them.

My new favorite title, Birth by Sleep (BbS) was an amazing game! This game featured 3 new characters, Terra, Aqua and Ventus. These are the playable characters of the game, in which you don't play using all three in a party, each character has there own story and game play style.

This game actually starts off with the antagonist Master Xehanort on Destiny Island. Who through secret reports we learn Xehanort himself actually is from Destiny Island and like Riku felt like a prisoner on the tiny island and wished to escape. He was chosen as a wielder of the key and trained with Eraqus under there master.
As a wielder of the Keyblade, one is taught to protect the light and forsake the dark. They travel among the worlds to defend the light, but in order to protect the world order, they hide in the shadows, the inhabitants of the worlds must not know of there existence, or that of other worlds.
To travel between worlds the keyblade could become a vehicle while its wielder donned armor to protect them from the "darkness" that lurks in space.
Xehanort began traversing the worlds without his armor. Feeling no fear from the darkness and wondering why fear or hide from it when one could control it.
He also some how learns of the Keyblade Wars that occurred thousands of years past. What is knows is that there was a fight between light and darkness for the ultimate power within Kingdom Hearts. It was said that the obtainer of this power could remake the worlds, using the ultimate key the x-blade. This blade can only form when an ultimate instrument of Light and Darkness meet. The War ended with unknown results, what is known is that the worlds were then separated, the warriors of Light and Darkness practically wipped out., we know this because it appears that Master Eraqus and his three pupils and Master Xehanort and his apprentice are all that is left of the wielders of the Keyblade. (as Master Yen Sid left his mantle of Master).
When we see Master Xehanort (also wearing the black cloak of the Organization) carrying something wrapped in a sheet. He is standing on the beach and looking out at the horizon, we see a faint glimpse of a younger Xehanort.
Wrapped in the blanket we see Ventus (who by the way Roxas looks exactly like), who appears to be comatose. Xehanort lays him on a trunk of a tree, and we are then taken to Ven's Station of Awakening. There is no image on time its blank and a chunk appears to be missing. A (voiceless) voice comes to Ventus and asks him whats wrong, Ven asks who he is, and is told he is a new heart, who was led her by a light. Ven responds that light once belonged to him but it was broken and he was losing it. The voice tells Ven to borrow his until Ven is stronger and can win his own light back. The two hearts connect and Ven's light returns.
From this point in the game we learn that Xehanort then took Ven, who now remembered nothing of what happened, to Eraqus. Informing Eraqus of his plan to use Ven in creating the x-blade he asks for forgiveness from Eraqus and request that Eraqus continue to train the boy and keep him safe.
We learn later that Ven's heart was damaged by Xehanort himself, when during a training session, Xehanort removed the darkness from Ven's heart in an attempt to create a being of Pure Light and Pure Darkness, to meet in battle and create the x-Blade. But Ventus heart was damaged by the process making him useless to Xehanort, even once he was revived (by the connection with the new heart) he was too weak to face Vanitas, who was the result of darkness being removed from Ven's heart.
Xehanort then sets a plan in motion to help make Ven strong enough to fight Vanitas. He allows Eraqus to train the boy with his other two apprentices to create a friend ship between the trio that he can manipulate and use to his advantage. He also upon meeting Terra, sees him as an "option" for another big plan he has.
Which leads us to the beginning of the game.
The order is designed to be played Terra, Ven then Aqua.
Using the Unversed we see Terra and Master Aqua set with the task of traveling the worlds, Xehanort knowing that if he was manipulated Ven would follow and become stronger than he could staying in the Land of Departure.
Terra, having something to prove after the Mark of Mastery exam, he sets out to prove to Master Eraqus that he can conquer the darkness within him and be worthy of the title Master. 
Throughout his journey he only seems to give in to his darkness more and more (with the help of the Manipulation of Master Xehanort). Along the way Terra finds his way to Destiny Island, lead there by a light. Where he runs into a young Sora and Riku, playing. He senses great light within Riku and performs the transference of power ritual on him, making him a Keyblade wielder. And swearing Riku to secrecy about what transpired between them.
Finally resulting in a clash between him and his Master, whom he uses the power of Darkness, although with good intention as it was to save Ven from Eraqus, to defeat him.
This leads to Xehanort wiping out  the Land of Departure with darkness. Terra follows him to the Keyblade Graveyard where the Keyblade War was originally fought, for revenge on Xehanort for manipulating him.
This ending in a fight between Terra and Xehanort, who once defeated releases his own heart with his keyblade and sends it to Terra and takes over his body.
Although Terra's will remains in his armor (he summoned last minute to try and protect himself from Xehanorts heart) to face Terranort. Who after defeat disappears.
This concludes Tarra's Story at which point you can play the next character.
Next up is Ven
Who follows Terra after receiving a warning from Vanitas that this will be the last chance Ven has to see his friend, cause once he leaves the Terra Ven knows will be long gone.
Ven travels to all the worlds having adventures of his own, eventually he runs into Xehanort, who tells him the truth behind his memory loss and who Ven is meant to be (the x-blade). He also tells Ven that Eraqus knew this and hid it from him.
Ven goes home to Land of Departure and confronts his Master, who now that Ven knows who and what he is to become, Eraqus cannot allow so he attempts to destroy Ven, and is stopped by Terra who fights his own master.
Ven now knowing that if he fights Vanitas it can create the x-blade, travels to the Keyblade Graveyard to destroy Vanitas and win back his heart.
He faces off against him with Aqua's help and in doing so creates the x-blade, but also resulting in Vanitas rejoining with Ven, and you have a battle over control of Ven's heart in the Station of Awakening.
Before the fight Ven actually quotes the line from the first game that Sora stated when he received the Keyblade back "my friends are my power!"
With Vanitas defeated the x-blade is shattered, along with Ven's heart as it was used to create the blade. And Ven falls to Darkness.
Leaving you with Aqua, the only one out of the trio to receive the mark of mastery.
Aqua follows to assist and keep an eye on Terra, to make sure he doesn't succumb to the darkness.
She was also ordered by her master to retrieve Ven and bring him home.
Aqua is probably the one character though that knows the least of what transpires.
She learns that Terra struck down their Master. Ven tells her when they meet in the Keyblade Graveyard, that if he and Vanitas fight he will become the x-blade.
Aqua runs into a young Kairi in Radiant Garden (later Hallow Bastion), her home before this all starts. After saving her from the unversed, with King Mickeys help. She places a protection spell on her to protect her should a great darkness surround her. Because she senses an important light within Kairi as well, unknowing that she is a Princess of Heart.
She also runs into Sora and Riku on Destiny Island. There she senses that Terra performed the transference of power ritual on Riku. And although she also senses a great light in Sora, she decides not to do the same for him stating "One Keyblade is enough to protect any friendship, I don't wish my life upon these kids." But she does ask Sora that should Riku loose his way, and get lost in the dark that Sora promise to find and protect him. Sora promises.
Upon meeting the others in the Keyblade Graveyard, after being sent there by Master Yen Sid, she faces of against Braig, a denizen of Radiant Garden, hired by Xehanort to cause a distraction to keep Ven and Aqua away from Terra.
She defeats Braig but is then knocked unconscious by Vanitas.
When she comes to she finds Ven standing there apparently comatose with the x-blade in his hands. When we realize that it is actually Vanitas in control of Ven's body, (while Ven and Vanitas fight within Ven's heart), She fights with Vanitas and as Ven defeats him within his heart and the Keyblade cracks she defeats Vanitas as well. This causes a massive explosion, as the x-blade holds unimaginable power. Aqua grabs on to Ven's hand and activates there armor.
Were taken to a scene then in space where we see Ven and Aqua floating, Mickey retrieves them and takes them to Yen Sid's tower where it is revealed that Ven is in a deep sleep and his heart has been lost, but if it could be returned Ven will awaken.
Aqua then takes Ven to the Land of Departure where using the technique she was taught for achieving mastery, transforms the Land of Departure to the Castle Oblivion (the setting for Chain of Memories). Where only she as the one who created the land will know how to navigate it, while others who venture there will never learn its secrets. Ven is kept there for safe keeping.
Deciding to find what has come of Terra, she calls out to him. He in turn calls back for help and she sees Radiant Garden being attacked by a mass of darkness.
She ventures there to find Terra now possesed by Xehanort, who has already lost some memories does not remember who he is. Aqua fights him and eventually Terra starts to show through, allowing her to defeat him.
Terra then uses Xehanorts keyblade and releases his heart, causing him to fall to darkness, Aqua jumps in and saves him, sending him back to the realm of light, but unable to save her self she gets lost in the realm of darkness.
This concludes the game, which after we see Riku and Sora sitting under the night sky. And Riku notices a single tear come from Sora's eye, although he is not sad. Sora responds that he feels some one out there is sad and he wishes to help. Riku states maybe all he needs to do is try.
So Sora focuses to hear what is being said.
Were taken then to Sora's Station of Awakening where he calls out to the person who is sad. A heart appears and we hear Ven's voice talk to Sora, who asks why hes sad.
He responds that he was lost in the darkness and a light called out to him (much like the beginning of the game!) He tells Sora that hes lost and has no where to go, Sora tells him well you can stay in my heart, and Ven agrees, and so we see that Ven's Heart rests within Sora's.
If you unlock the secret movie at the end you are shown Terranort in Radiant Garden, discovered by Ansem and some of his apprentices. With no memories of who he is, only one word comes out of his mouth, Xehanort, and Braig one of the people present smiles knowing his previous boss succeeded.
We then see Braig and Apprentice Xehanort walking around the castle together, as well as Ansem and the young boy Ienzo eating sea salt ice cream and walking through castle, and Ienzo takes notice of Xehanort an Braig. We then see a scene between the real Terra, and old Master Xehanort. Terra states that Xehanort is going to loose the fight for Terra's heart and Xehanort mentions that another has set foot there making Terra stronger.
Lastly we are lead to Aqua who is wondering around the world of Darkness, unprotected as she willed her armor and her keyblade to return Terra to the realm of Light.
She is also seen wielding her Masters Keyblade she retrieved from the Land of Departure and used it to transform it to Castle Oblivion.
A bunch of giant creatures of Darkness appear (the same Sora first faces in KH) and Aqua appears ready to give up. She is then saved by Terra and Ven's Keyblades giving here strength to continue to look for a way out.
Now it is assumed that time passes differently hear as she ends up on the same beach that Sora and Riku ended up on at the end of KHII, and she happens to meet Ansem the Wise, who is shrouded in one of the Organization cloaks.
He tells her of the goings on of the worlds and the boy with the key to save them. She inquires who this boy is and we are shown characters Sora has previously met. Namine, Roxas, Axel, Xion, Ventus and Terra, who all call out the same name. Sora!
Realizing this was the little boy she met on Destiny Island she realized she could not save him from the fate of the Keyblade, the light had plans for him.
This is where the game ends!

This provided some huge incite to some of the unanswered questions of KH.
Such as how did Sora come to wield the keyblade? It is my theory that Sora having connected his heart with Ven's became a great source of light and as such was chosen by the keyblade itself.
We thought originally that he was wielding Riku's keyblade because Riku chose Darkness. And while this is not fully explained, I believe this isn't the case as in II Riku wields his own Keyblade.
I also believe there are two was to become a wielder of the Keyblade. Be chosen, or the transference of power ritual performed on Riku by Terra.
A question was raised when the name of Xehanort was revealed and he was an old man, and how this could be as he was young in KH, which remember is 10 years after Birth By Sleep? This is answered by Xehanorts possession of Terra, he acquires a younger body therefore is young once more when he faces Sora.
We see why Kairi ended up on Destiny Island? The protective spell that Aqua placed on her should darkness come. Well we know from the previous titles that Radiant Garden gets consumed by darkness, becoming Hollow Bastion, the charm activated Kairi was teleported to Destiny Islands, a side effect of having no memory of where she came from. She then meets her protector there Sora.
But it also brings up a lot of other questions.
What is Xehanorts plans for the future? Where is all this information leading to and to what end?
Will Sora rescue, Ven, Aqua and Terra, and the many others who have disappeared.
What really is Kingdom Hearts and the x-blade.
Will there be another Keyblade War as it seemed Xehanort was trying to recreate it?
Things to ponder!

One of the other things this game gives some incite to, we get to meet some of the Organization XIII's Nobody's, Somebody's.
Braig= Xigbar
Dilan= Xaldin
Aeleus= Lexaeus
Even= Vexen
Ienzo= Zexion
Ven also meets Lea and Isa, who in the future become Axel and Saix.

Square has also release a Final Mix version which at the end had an extended secret movie.
Birth By Sleep is considered Kingdom Hearts Zero in the numerical sense being the beginning of everything.
In the newer secret movie it shows 0.5 and ends with the words Birth By Sleep: Vol 2. Is it possible we may see a sequel to BBS? The events of the game did not start us off with KH so there are still some things that happen that could lead us to KH?
So exciting!
Next up Picture Time!! Birth By Sleep. Followed by another side story following KHII, and the last title to be released so far, until next years Kingdom Hearts: Dream Drop Distance, a future title being released for Nintendo 3D's in 2012 along with another title said to be the last before KH III (the possible Birth By Sleep Vol 2?). Kingdom Hearts: Coded.