Prologue
"Huahhh!" Riku bellowed as he dashed forward. The Way to the Dawn swung swiftly and clashed against the Kingdom Key.
"Ergh…Riku, what's the matter with you?" Sora demanded, struggling under the weight of Riku's swing. Sora shoved away Riku's keyblade and backflipped out of range. "Knock it off!"
Riku had been acting strangely for several days now. He seemed to have grown more irritable by the day. It was finally today, a short walk across the island, that set him off, attacking Sora out of the blue. No matter how badly he wanted to believe his best friend was stronger now with all they'd been through, the man standing in front of him seemed to contradict that. He was in such a blind fury right now, no words could even form from his tongue.
Riku pulled back his weapon, filled it with energy, and shot out three homing fireballs. Sora braced his key blade to block, waiting to take the force of the flames only for three boulders of ice to neutralize the attack instead. A small figure spun in the air to land in front of Sora. "Huh? Mick-…Your Majesty!" The enraged Riku lunged and swiped at the mouse king in rapid succession, but King Mickey's small stature proved too agile to hit, ducking and flipping between swings.
"Riku! You gotta snap outta this!" Mickey implored, locking blades, but Riku remained mute. "Sora, why can't he respond?"
"I don't know," Sora replied, jumping back into the fight. "I can't get anything through to him! He just attacked out of nowhere. Do you think the darkness is back?" Both key blade heroes teamed up against their opponent, yet Riku managed to hold them both off on his own.
"Wait, Sora, look!" Mickey declared during a moment of pause. He pointed a single gloved finger toward Riku's eyes. A strange red haze shrouded the upper portion of his head. "I think I know what has to be done. Forgive us, Riku," the King said before flipping over him, knocking the butt of his key blade into his forehead and knocking him unconscious. Riku collapsed to the ground lifeless, leaving Sora and Mickey standing over him.
"Do you know…how to help him?" Sora knelt down and hovered his weapon over Riku's body. "I'm not detecting any darkness in his heart."
"That's because it's not in his heart. It's in there," the King replied.
"In…his head?"
"His mind. Lots'a stuff can affect our hearts, but there are fewer forces that can take over our minds."
"So do we have to get in there and help him out?" Mickey's expression turned somber.
"I hate to admit that I don't have any experience in this field. If we head in there, I have no clue what we'll find in there…" Sora placed his hand on his hips and a smile on his face.
"C'mon, Your Majesty. I've had lots of adventures. I can handle myself." Mickey nodded.
"Right, but I'm comin' with you!"
Sora grinned. "It's about time we had our own adventure!" Both wielders crossed their key blades and tapped Riku's forehead. As usual, a small pinprick of light emitted from the tips, steadily growing brighter and brighter until it entirely filled their vision.