Walkthrough:Kingdom Hearts II/Hollow Bastion
 First Visit
Hollow Bastion will serve as your homebase in this game. When you first appear Sora, Donald and Goofy will run up to a stone wall and will regonise this place as Hollow Bastion, with Goofy comenting on that this world is different, somehow. He'll then spot some Soldiers on the rooftops of the shops, and will comment that they might have to do some fighting.
Once you regain control of the party, head down the stairs and you'll notice some shops, along with a Moogle shop, which can be used to cash in your Synthises items. You should also speak with Scrooge McDuck, who is trying to remember an ice cream flavour, but is having trouble with it. Goofy also reveals to Sora that Scrooge is Donald's uncle, and that he is very rich.
 Second Visit
You will be automatically taken to this world after visiting any two of the following three worlds: The Land of Dragons, Beast's Castle, Olympus Coliseum. You cannot leave this world at all during this trip.
Turns out that Merlin summoned us over for a suprise: he found the 100 Acre Wood's book in the Zero District and, knowing that Sora is good friends with Winnie the Pooh, decided to summon the party over to break the news. However, Merlin soon heads off to find Leon and the others. Sora decides to go into the book and see how Pooh is doing.
Gameplay resumes. The door outside is locked, and the save point will not let you leave this world. To go further in with the story, talk to Donald, and enter the book...
Sora had been chucked out of the 100 Acre Wood after Pooh suddenly froze in midair. Turns out that Donald used his magic to summon him, due to the Heartless threat. Sora then ran outside, leaving the book to be stolen by three Soldiers.
As it turns out, the Heartless tore out some pages, affecting Pooh's memories, explaining why he cannot remember Sora or Piglet or any of his other friends. The party agree to keep this a secrect with Merlin for now. Just before you leave, Merlin will grant Sora with the power to Summon allies in battle, like with Mushu and Simba last time. Your first summonable ally will be Chicken Little.
After the cutscene ends, a brief tutorial will show you where you can summon, and how. You'll then automatically leave Hollow Bastion.
 Third Visit
You'll be required to visit this world to further advance with Disney Castle. Upon landing, a cutscene will begin. Something is wrong in the castle, and Goofy sugests that they get Merlin to help. Merlin appears, and when he asks if the party has learned anything since the last visit, Donald explains that the castle is in danger, and Queen Minnie needs his help. During this cutscene, you'll be automatically taken back to Disney Castle (via Merlin's magic)
 Fourth Visit
The party starts again in the shops, there they spot Heartless and Nobodies all over the place. After the cutscene, head towards the Moogle Shop, where a cutscene with Cloud will play. After that, head towards Merlin's House, where it's revealed that Leon and Aerith have found the computer that Ansem the Wise used during his reaserch. After the cutscene ends head towards the Bailey, where you'll meet a trio of fairies who appear to work for Maleficent
Soon, you'll reach the exit of the castle, where a save point and some more treasure chests await. Aerith will explain that the king is very interested with the computer. The cutscene ends. Head to the entrance (this is your last chance to save the game, though). Inside, a strange blue monster will climb the ceilings, but the party does not see him. Head through until you reach the back, and then you'll find yourself in a room... without a computer. A woman named Tifa will enter the room and ask if the party has seen "a guy with spiky hair"? Sora pulls his hair to show it's spiky, thinking she wants to see HIM, but Tifa says "spikier", which the party delines. Tifa will look around the room, but soon gets frustrated and punches the wall... so hard that it causes a rumble. Tifa then leaves the room, and Leon appears.
Talk to Leon, and he'll reveal a secret passage to the computer. Head towards the computer room, and a cutscene will begin. Sora attempts to ask the computer for the locations of Riku and Kairi, but Leon tells him to be easy, since Sora, how's probably never seen a computer before, can break it. Suddenly, the blue monster from eariler, Stitch, appears and lands on the keyboard. Donald then tackles him to chase him off. He turns around in an angry matter, but suddenly, a voice claiming to be the Master Control Program is alerted, explaining that further violation of the computer will result on punishment. However, Donald, while attemping to get off, accidently steps on another button. This angers the MCP, who then puts the trio and Leon under arrest.
A few seconds later, Leon, who is at a safe spot, suddenly notices a beam coming from the back of the room, and tells Sora and his friends, who are in danger, to run, but it was too late, as the trio are hit by the beam and pulled into the computer system, in front of a horrified Leon.
 Fifth Visit
 Sixth Visit