*Third Person POV*
Heartless Y/n snuck through the castle, careful to crawl along the roof beams and stay away from any Heartless that could see him. He stabbed his claws into wooden beams, hid under tables, behind bookshelves, and anywhere he could remain unnoticed.
Normally, he would've just torn through his opponents as his instincts were telling him. But something was different, a gnawing feeling in the back of his head that told him that it was best to remain hidden.
And so, as he crawled along the floor to avoid being seen by some patrolling Enforcers, he noticed a small brass grate against the wall. He reeled his feet back and kicked the grate inwards, revealing a completely dark ventilation shaft. He slowly crawled inside, disappearing into the darkness.
He was immediately shocked, as there was no floor beneath him. He dropped down for a few feet, before slamming against the grate hard. He pushed himself back into a crawling position, shaking his head to rid himself of the dizziness that came with falling.
Darkness was nothing to him, in fact it was home. The disorientation he had been feeling throughout his journey through the large castle had been caused by this magical light that he had sensed. It was warm, comforting, and seemed to call out to him specifically.
It felt like a friend.
And so, as he crawled through the ventilation system, Heartless Y/n followed his sense of this strange light. He let it lead him through the shaft, further down into the castle. Eventually, he could sense that he was deep underground, and he heard speaking from below him.
*Y/n POV*
"KAIRI!"
That's the Keyblade Girl, Sora. Was she the source of all this light? No, I would've sensed this before.
I looked out of the grate below me, seeing Sora holding onto a short girl with brownish-red hair. It was the same girl I saw in that strange castle, though... why is she asleep? That girl is screaming at the top of her lungs.
Kairi, as I assumed her name was, was turned over and I managed to see her entire front. My mind seemed to explode, and my vision went white.
{Flashback}
"Y/n!"
I whipped around quickly, seeing Kairi flying through the air at me.
"Kairi wait-!"
The wind was knocked out of my lungs, as Kairi crashed into me and sent me sprawling against the sand. She laid there on my chest, as I let out a weak groan.
"Kairi..."
"Oh come off it, Y/n," She said dismissively, "I'm not heavy. Or are you trying to say I'm fat?"
"No, no, of course not!" I quickly said.
"Aww, you're so sweet," She said, snuggling into my chest, "My hero."
Suddenly, she pressed her lips against my cheek, before pushing herself up and taking off down the beach. I watched her leave, as I laid on the sand in a daze.
{Flashback Over}
As I was trapped in my daze, I failed to notice as the other girl, Riku, walked up to Sora and Kairi. However, something was off.
Her clothes had changed, and a Heartless symbol was present on her chest. This was definitely not Riku, but Ansem almost entirely.
"That girl has lost her heart," She said ominously, "She cannot wake up."
"What? You..." Sora confusedly breathed, "You're not Riku."
Congratulations, you've finally caught up.
"The keyhole can not be completed so long as the last princess of heart still sleeps."
She jumped down from her perch, slowly floating to the ground and landing in front of the large portal device behind him. She seemed even more intimidating, as her keyblade gleamed in the light slightly.
"The princess?" Sora repeated, "Kairi... is a princess?"
"Yes, and without her power," Riku-Ansem explained, "The keyhole will remain incomplete. It is time she awakened."
"Whoever you are, let Riku go!" Sora yelled, "Ger her back her heart!"
"But first, you must give the princess back her heart!"
What? Give the princess back her heart? How?
Did Kairi's heart latch onto Sora somehow?
Suddenly, Sora's chest exploded with a red light. She fell over to her knees, clutching at her chest as the duck looked on in fear.
"Sora!" The duck yelled.
"Don't you see yet?" Riku-Ansem questioned, "The princess' heart is responding. It has been there all along. Kairi's heart rests within you!"
"Kairi... Kairi's inside me?"
"I know all there is to know," Riku-Ansem boasted, "I truly am a genius."
"W-who are you?" Sora asked, looking up at Riku-Ansem.
"It is I, Ansem, Seeker of Darkness!"
Riku-Ansem began to walk towards Sora, the duck jumping out in front to protect her. He was easily smacked away, shoved through a magical barrier that kept him out. Riku-Ansem came close to Sora, pointing at Sora.
"So, I shall release you, princess," He/she monologued, "Complete the keyhole with your power, and lead me into everlasting darkness!"
She/he raised his/her keyblade to strike Sora, and my vision slowed. My body seemed to move on its own, as danger became apparent.
I kicked the grate out from under me, using the vent to swing myself towards them. As I was flying through the air, my keyblade appeared in my hand. It felt strange, as it no longer burned my hand as I gripped it tightly. I shot through the air, striking Riku-Ansem's keyblade with my own and sending us sprawling.
I quickly stood up, holding my keyblade out in a defensive stance in front of Sora.
*Third Person POV*
"Y-y/n..." She said, clearly forcing her words through her pain, "Y-you..."
"Sora," Y/n said, looking back at her, "Take care of Kairi for me."
Riku-Ansem rushed towards Heartless Y/n, releasing an angry scream as he swung his keyblade through the air. Heartless Y/n matched the attack with a defensive strike of his own, and sparks flew as the battle began.