In Kingdom Hearts, you joined up with Beast at Hollow Bastion to find his wife Belle, who also happened to be one of the princesses of heart. In Kingdom Hearts 2, you will get the oppertunity to join Beast and Belle in their castle.

Once you enter Beast's Castle/world, you will come upon a shadow heartless. Sora, Donal and Goofy decide to follow it throughout the Castle. In a short while, you'll find yourself surrounded by tons of shadow heartless, until Beast makes his grand entrance and gets rid of the heartless. When you thought you were safe, Beast attacks you as well! Before you know it, Sora, Donald and Goofy are out on the floor and Beast has disappeared from the room, taking the Rose, which was in the room, with him.

As a confused group, you eventually find Belle in the castle, which lets you in on whats going on. Belle explains that Beast is acting very mysterious and has even locked the entire Castle's staff in a dungeon. As Belle is scared, this is where Sora and company comes in to help out. Once you journey throughout the castle, you find a 'Dresser' who managed to not be seen by Beast and become imprisoned. He tells Sora the location of the imprisoned staff. Once arriving to free these imprisoned staffsman, you must battle a boss; but any boss; a door!

Speaking of bosses, Xaldin, an Organization member, is in this world. Xaldin takes the responsibilty for manipulating Beast and later, kidnapping Belle. Eventually, you will battle it out with Xaldin alongside Beast, and hopefully, rescue Princess Belle.