Hey guys~ Well, here's my first fanfic! Yay~ Enjoy and don't forget to review in the end!

READ THIS FIRST: Just so you know, the main character is a girl, but the other characters don't know. They think she is a boy. So 'she' will often be referred to as 'he'. Try and keep up. I'll try not to make it too confusing...

I don't own any of the characters...not even Riku...he belongs to Square Enix. But the mysterious character is mine!

She came upon the castle, and the giant gates loomed over her. Castle Oblivion. She searched everything about this world. The Keyblade Masters, Kingdom Hearts, Sora, the Heartless, and most recently, the Nobodies. Fully prepared for her mission, she pushed the doors open with ease and took her first steps into the world that would forever change her life.

Riku slowly walked down the deep corridors of the castle. His black cloak was on, the hood shrouding his face in darkness. The conversation with Ansem was still embedded in his mind.

"You can't run from me, Riku…I am now apart of you!" Ansem deflected all of the attacks Riku threw at him. He blocked his attack and chuckled as Riku grunted and fell to the floor.

"I'll never be you! I'll fight you, and I'll win!" Riku proclaimed. He jumped one last time on Ansem, but Ansem disappeared right as his blade came down. His menacing laughter echoed down the hall.

He didn't know what to do. He was brought to this place, and told that Sora was here. But how could he ever face him, knowing what he did? Lost in his thoughts, Riku almost ran into some trouble. Three of the organization members were in one hall, crowding another member. He didn't know much about this place or its inhabitants, but he knew they were dangerous. He hid behind the pillar, and listened.

"Huh, so this was the intruder that he was talking about! Who knew such a powerful aura came from such a small body! Ha ha!" The biggest one out of the three laughed loudly, throwing back his hood, revealing spiky light brown hair and hard face.

The other two pulled down their hoods, revealing themselves. The second tallest had long blond hair and his eyes looked slightly off.

"Now, now, what do we do with this one, eh? He said dispose of him, but let's have a little fun, huh?" His laughter rang through the halls, sounding slightly deranged.

The smallest one had short lavender hair and only sighed. "Whatever, do what you want."

Riku looked at the 'intruder'. He really was small compared to the other three. He didn't stand a chance. Yet he didn't say anything. He also wore a black cloak, like Riku and the others. But he didn't do anything. He didn't deny their words, or tremble like others would. He stood silently, taking in the scene.

'Ugh, how bothersome…' she thought. 'I just walked in not even five minutes ago, and I was already caught. But maybe…'

She was too lost in her thoughts to notice that the three men in front of her had stopped talking. She looked up, only to notice that the biggest one had drawn out a large weapon.

"How troublesome…" she finally said.

"Troublesome?!" he shouted. He was already upset that he hadn't intimidated this guy, but now he was a bother? "I'll show you troublesome!" He shouted out in fury as he lunged for the little person.

As fast as he charged the intruder, he was flying across the room. The large man smashed his back against the wall, leaving a gaping hole in the wall, and he fell loudly to the ground. The other two stood shocked. This infiltrator had the strength to lift and throw that huge man across the room, and enough power that he left a hole in the wall?

Riku was frozen in his spot. What just happened? It was so fast, he didn't even see the intruder's arm even move?

Did it even move…?

The intruder sighed once more, and was left with the other two, who still stood silently.

"Why you little….! No matter. Lexaeus was being stupid. Clearly," the blonde man eyed the intruder and smirked, "we underestimated you."

The intruder merely crossed his arms, and in a condescending tone, he said, "Clearly."

"Well, I shall not make the same mistake." He drew out his shield like weapon and eyed the intruder. Then he quickly charged, only this time, he jumped up high and tried to strike the intruder down. But the spot was empty as he came down. "Wha…?" The shocked man could stop himself from the blow. He crashed to the ground and fell unconscious, just like the other man.

The small man was left to face the infiltrator, who had dodged his attack and stood five feet away from where he was originally.

Zexion stood silently, not showing the shock within. When did this person even move? He hadn't seen a step being taken, let alone watch as this person was five feet away. 'I better not take any chances….' He thought. 'Someone still needs to tell him what's going on….'

"Zexion." The intruder finally spoke. Shocked, all Zexion could do was stare. "Tell your leader that as soon as I entered this castle, his fate was decided. This organization was destined to end by my hands. Now…go."

For some reason, Zexion felt his body moving on his own, and he created a portal for himself, directly to Xemnas, leaving the intruder and the two unconscious Nobodies.

Sighing deeply at the slight annoyance, she removed her hood. Her long black hair flowed down her back. Her slim face was hard and showed no emotion. The only questionable appearance about the girl were her eyes. You couldn't see them. She wore a thick blindfold, covering her eyes completely, but she could still see through them. She looked at the two unconscious bodies, and waved her hand across them. Two black portals appeared, taking their bodies away. She stood and stared at her current position.

'According to the three annoyances, they felt my aura. However, I completely masked my aura. That means that there is another intruder with a large amount of power. He said that I have to protect a boy my age by the name of…what was it?...Riku?' she thought silently to herself about the mission assigned to her. Then, she felt something. Her face darted down the hall, sensing a small amount of power. 'Ah…there he is…' she smirked, 'how cute. He's trying to hide from me…' She chuckled to herself. 'Don't worry, boy, I won't hurt you. For whatever reason, my duty is to protect you.'

She pulled her hood over her head and created a portal for herself and silently slipped away.

Riku stood staring at the current situation. The blonde haired man, Vexen, if he remembered, was also quickly defeated by the intruder. He watched the confrontation between the other member and intruder. Then he was shocked to hear the voice instead.

"Zexion, tell your leader that as soon as I entered this castle, his fate was decided. This organization was destined to end by my hands. Now…go."

Riku watched as the other member silently obeyed the infiltrator. Then he paled. Would he be the next victim? He quickly tried to mask his aura, but at the same time, he watched the intruder. He noticed that although he was wearing the same black cloak, his gloves were fingerless. He also had a slim figure. He watched the lithe figure as it waved a hand over the unconscious members, sending them away. The intruder then pulled the cloak off, revealing itself, however Riku was too far away to see the face. He watched as the intruder just stood for a moment. For a brief second, he felt as if his eyes were in his direction, but brushed it off. Then he heard a small chuckle. His face was drained of any color left in them. He definitely did not want to mess with this man. He seemed like a very dangerous person. Then he watched as he pulled his hood over himself, created a portal for himself and slipped away.

As soon as he left, Riku breathed out a sigh of relief and dropped to his knees. He hoped that he would never encounter this person ever again in his lifetime.

How wrong he would be.

Yay! First chapter up! I'll try to upload more chapters soon. Please review!