And yes, I know that neither the characters nor the song the story came from (if applicable) belong to me. They are Square's. Yay Square! (and Disney in this case) But the lament/story continued is mine.
The door was now closed. He no longer had the key to open it. The mouse did. His "friend" did. But not him. He wanted it back. He was the real Keyblade master, everyone knew that. Yet it was denied to him by a simple misjudgment of right and wrong. It was a simple mistake. All people, including heroes, make mistakes. Only this one had more apparent effects upon every single world. It was this mistake that nearly caused an apocalypse, this mistake that cost him the one he held dearest in the end. It was this mistake that had put him here, driven to the edge.
"Take care of her."
Those were his last words before his only ray of hope vanished on the other side of the door. He did not know what had happened to her since that day, and he was beginning to care less and less. She was forever lost to him now, placed instead into the arms of he whom was once known as "friend." They had both abandoned him in one way or another. He did his best to save her, but as it turned out, such efforts were not good enough to keep her in safety. He did owe his friend gratitude for doing what he could not, and gave up his adoration to the true victor. Though his friend agreed to comply with his wish, he couldn't help but feel there was a touch of arrogance involved, a sort of gloating over the prize. When he next saw his friend, he would prove he had the right to bear the key, the right to save the world, the right to protect the girl, whether anyone liked it or not.
But there were obstacles in the way of his road to revenge. Along with the door being shut tight, he was trapped with a swarm of raging Heartless and a mouse that looked to the light far too often for his tastes. The former were easy enough to defeat. The fact that they could respawn quickly was only a minor setback. The rodent however was much too aggravating. It was a decent fighter, as proven in many partnered battles with the dark creatures. He respected its ability to wield the Keyblade and to fight. In fact, there were really only two things that bothered him about the mouse. First and foremost were its endless lectures on the power of the light and its strength over darkness. He cared not to hear such things. He knew he had done wrong. He knew full well the consequences of his mistakes by now. But he also knew that being talked down to -by a rat, of all creatures- was not the cure for his "issues with the light." In fact, it only made them grow in magnitude. Worse yet, the foul annoyance had the Keyblade, the one thing he desired above all else. His armaments during the time were a simple wooden sword and any dark powers acquired during the period when he was in control. The mouse forbid him to use the latter, so in respect he relied on his brute strength more often. It never abandoned its weapon and slept rarely, cradling the key in its slumber. The days grew longer and harder behind the door, destruction of countless Heartless being the only entertainment available. He couldn't stand his company. Few opportunities arose to reclaim his rightful weapon, and even when they did, the time spent readying to strike was all that could be spared at once. The rodent grew even more tiresome, its rantings becoming routinely repetitive. Within, he wanted to bust from his ivory-gated prison, away from the mouse, to inflict misery upon those who had done likewise to him. And soon enough, another chance would come... All he needed was the key...
Riku would take back the Keyblade, or die trying.