After being forced into the conflict of the gods by three others, the Keyblade warriors, Nick and Kairi, and their masters and friends, Riku and Matthew, returned to the Mysterious Tower, home of the great sorcerer Yen Sid. And soon, after retaking his Mark of Mastery exam, Nick became a Keyblade master…

Yen Sid: Nick. In light of recent events, your actions in the conflict between Cosmos and Chaos, I decided to let you retake your Mark of Mastery. And because of your efforts, I now dub you a true Keyblade master.

Nick: All right! Er… I mean, thank you, Master Yen Sid.

Kairi: Well done, Nick! You did it!

Nick: Thanks, Kairi. What do you guys think? After all, you two were the ones who set it up for me.

Riku: You did well, Nick.

Matthew: Say it again. What were the keywords to get you out?

Nick: (sigh) My friends are my power.

Matthew: Yes! I knew he would say it again! Mog, we rock, don't we?!

Mog: You bet, kupo!

Nick: Honestly, you two are exactly like each other. Anyway, I need a vacation. See you guys soon!

However, when Nick went through the door, he didn't find himself in the tower but on a ship…

Nick: Huh? How did I get here? Never mind. I'll just relax here.

As he said that, he sat down on a chair, rested his head and hand a nice drink. Meanwhile, back at the Mysterious Tower, Yen Sid sensed something was wrong…

Yen Sid: Riku, Matthew, I need you.

Riku: What's wrong?

Yen Sid: Something has grown amiss in numerous worlds. And they all seem to be connected to one place, the Koryuji mansion.

Matthew: Koryuji…

Mog: … mansion?

Yen Sid: Yes. Now, let me explain fully. The worlds are engulfed in a quiet chaos. Shadows lurk behind the unchanging peacefulness of everyday life. Twisted beings writhe unseen in the darkness. Mysterious dimensional portals connect the real world to others more fantastic. But, with the passage of time, people have eventually come to understand and even accept these things as a part of their daily lives. All without knowing the existence of the people and organisations fighting the true evil. Now as for the Koryuji estate, there is a certain family that has worked in secrecy behind the scenes throughout history. Recently, the treasure that the family have been protecting, known as the "Portalstone" has been stolen. It is currently unknown who has stolen it. Now, I need you two to help the Koryuji family to recover the Portalstone.

Riku: You can rely on us.

Matthew: Mog and I will go get Nick and then we'll head off.

Matthew and Mog left the room but instead of being in the tower, they ended up in a desert with a single pyramid…

Matthew: Um, Mog, where are we?

Mog: I think we've just been transported to another world, kupo. But, it's pretty hot out here, kupo. Let's go inside the pyramid.

Matthew: Let's just hope you don't evaporate before doing so, Mog.

After a while, at the Mysterious Tower, Riku and Kairi were getting worried about the friends' whereabouts…

Kairi: It doesn't take this long to get from outside and back here, does it?

Riku: No. Not even to get Nick.

Yen Sid: It's just as I feared. By going through that door, Nick, Matthew and Mog have been sent to a different world.

Kairi: What?!

Yen Sid: Riku, go through that door and you may find your friends.

Riku: Right.

Kairi: Master Yen Sid, let me go too.

Yen Sid: No, Kairi. If something were to happen to you, then everything will fall apart. We can't afford to take that risk again.

Riku: Don't worry, Kairi. I'll be back soon.

Kairi: Okay, be careful.

Riku went out the door and, just as Yen Sid said, Riku ended up in another world as a city…

Riku: Yep, this is definitely another world.

The same can be said about another friend of theirs, Sora. He had been to Traverse Town after their first Mark of Mastery exam to see the Dream Eaters. But, he wouldn't stay there for long…

Sora: Huh?

In front of him, he could see a "Frootz Cat" Dream Eater going crazy about seeing something strange…

Sora: Whoa, what's wrong?

The Dream Eater points toward a strange portal in the middle of the First District…

Sora: What's that? Aaaaah!

Before Sora could get away, he was sucked into the portal and reappeared at a strange mansion…

Sora: Ow… Huh, where am I?

And then, Sora saw a young girl come out of the mansion…

Mii: Whew, guess I'm last out of the house. I suppose I'll be saying goodbye to this old mansion for a little while. But I gotta say… What's taking him so long…?

Sora: What is she wearing?

And then, a man in a suit came to see the girl…

Kogoro: Hey there, m'lady. Finished locking up yet?

Sora: And who's that guy?

Mii: Ugh! You are so late! You have to be the laziest private tutor in the world! I've already given up on you actually teaching me anything useful. But the least you could do at a time like this is help me out a little, Kogoro!

Kogoro: Hey, m'lady, don't get so worked up. It'll make your skin break out again.

Sora: Break out?

Kogoro: I just had a bit of an issue I needed to clear up at the office.

Mii: Oh, reeeally? Look, I know you never actually get any detective work done.

Sora: He's a detective?

Mii: Why don't you drop the act and concentrate on trying to teach me something, huh?

Kogoro: Ah, you always were one of my touchier pupils.

Sora: He's her teacher?!

Kogoro: This particular issue though… I think I know what it is about.

Mii: What issue? What are you… You mean the stone that was taken from my mansion?

Sora: A stone?

Kogoro: Shh! Later, m'lady! Someone's coming!

Sora: How'd he know I was there?!

But instead of Sora being noticed, four strange being appeared in front of Kogoro & Mii…

?: Hoh hoh hoh! By the name of our master!

Sora: What are those things?! They're not Heartless, Nobodies or Dream Eaters!

Mii: Ahhh! What're these monsters?!

Kogoro: Looks like our culprits haven't given up robbing you blind just yet.

Mii: Ugh! We gotta catch 'em and find out where they took the stone! Kogoro! Let's get 'em!

Kogoro: As you wish, m'lady. I think now's the time to show off some of my Tenzai Ninjutsu.

Mii: Hee hee! Let's see if it's anything worthy of my praise for a change.

Kogoro: Hopefully, a little roughing up is all this is going to take. But somehow I get the feeling this is just the beginning of things.

Sora: They're going to fight them but I can't just sit back and watch. Look out!

Sora summoned his Keyblade and knocked one of the monsters away and forced it to retreat…

Kogoro: Who are you?

Sora: I'm Sora. A Keyblade wielder.

Mii: A Keyblade. Kogoro, have you heard of those things?

Kogoro: No, I don't think I have.

Mii: Anyway, my name's Mii Koryuji.

Kogoro: And I'm Kogoro Tenzai.

Sora: I can handle these guys so get back.

Mii: No way! We can fight too!

Kogoro: Right. Let's get started. Do you have any weapons on you, m'lady?

Mii: Sure do! I thought something like this might happen.

Kogoro: I wonder about the wisdom of giving guns to high school girls, though.

Mii: Well, everyone in the Koryuji clan has them. We're a family of fighting monks! Besides, what kind of detective carries a sword around like that?

Kogoro: A smart one, that's who. It's just the thing for dealing with evil thugs. Plus, my sword skill qualifies me to teach you martial arts, no?

Mii: Yeah, but I wish we'd move on to ninjutsu sometime.

Kogoro: You're still only in high school, m'lady. A few more years, then we'll talk.

Mii: Well, promise to teach me real ninjutsu, okay? Not any of your usual goofy stuff.

Kogoro: We'll see.

Mii: I showed that stuff off to the other girls in school, and they laughed at me!

Kogoro: Ah, yes, your friends on the cheerleading squad? They are not ready yet. Anyway, let's see some of you martial arts. You're a natural, aren't you, m'lady?

Mii: Of course! I hate composition class, but I'm killer at fighting!

Sora: All right, let's go and take them out!

After a while of fighting, Kogoro, Mii and Sora defeated the enemies and Sora explained how he came here…

Sora: And that's what happened to me.

Mii: Maybe it has something to do with the thieves that just came here.

Kogoro: I still wonder why they even bothered coming back.

Mii: They already have the stone. There's nothing left for them to take.

Kogoro: They have to be here for a reason. We better take a look around. Sora, would you like to help?

Sora: Well, I don't think I can get back. I think I'll help you guys out.

Mii: Oooh, trying to play the master detective again aren't you?

Kogoro: That's because I AM a detective, m'lady. Hmm… it wasn't the Portalstone they were after…

Mii: What else is there other than the sacred treasure of the Koryuji clan?

With many questions on their minds, what could lie in store for our heroes? To be continued…