Disclaimer: I don't own the rights to any of the CLAMP works.
The sounds of a large city in chaos echoed around them, but they paid it no heed, too wrapped up in their own conversation as they were.
"You don't need to know what I just said." The doppelganger looked to Fuuma. "You only need to know this: this world will not remain has it is. When the last earthquake wipes out this civilization with its destructive force, an acid rain will come to cleanse the world of all its rubble. You need to take my payment and leave this world before that happens."
"And you?" Fuuma asked. "What will you do?"
"I'll leave before you do," the doppelganger said. "I can't remain in one place, that's the price for the sin brought forth by my wish." The doppelganger then turned his gaze towards the vampire. "It's worth it, though. Every sin is worth bringing the one I love back to life, because the alternative is just... unbearable."
"Why did you kill him?" Kamui asked. "If he was your best friend and you love him so much, then why? You speak as if fate had taken control over your very body, using your hand to plunge that sword into his body without your consent.
The doppelganger smiled emptily. "I didn't have a choice. The choice to protect or destroy was given to him, and I was delegated to be his opposite. Though I knew what I was doing, I couldn't feel it. The part of me that cared was... suppressed; and another, much more ugly part of me took control."
"Are you saying that you aren't to blame for your best friend's death?" Kamui demanded.
"You meant to ask: do I not have free will in this? The truth is, that I don't know. Yes, I was the one who murdered him; I'll own up to that responsibility. But a part of me didn't want it. That part of me was suppressed, and I couldn't reach it, not until I'd ran him through with that accursed sword. When I killed him, the part of me that was held back came back to me, and I realized how much he meant to me."
The doppelganger gave Kamui a determined look. " That's why I'm gonna fix this. When I have broken the ultimate taboo, brought the dead back to life, and destroyed reality's foundation... that's when I will have proof of my free will. That's when I will truly have surpassed my destiny."
Kamui felt his heart constrict at that bold declaration. "I said today that I wanted Fuuma to win," he confessed, "I want free will to prevail, because the other option is to be at the whim and mercy of something out of my control; and wouldn't that be sad? So," he took a deep sigh, then decided, "I will help you bring back your loved one," his gaze strayed towards the body of Subaru's lookalike, "and keep my promise towards that girl I met."
He started towards the two bodies, but Fuuma held him back by his arm. "Kamui, are you sure?" the hunter asked.
Kamui gave him a pensive look, before nodding. "I don't know why, Fuuma," he said softly, "I feel like I have gaps in my memory preventing me from understanding the full truth, but... I think this was already done." He frowned, turning his attention back to Fuuma's doppelganger. "I have a theory; I could be right, I could be wrong; but this must be my past, am I right?"
The doppelganger lifted an eyebrow. "You're right," he said, "but how? You can't know this through your memories. You don't have those memories."
"I don't need memories to know," Kamui sneered. "It can be deduced from the evidence. Subaru was my twin, but he told me he could no longer be my brother, because my true twin was waiting for me. The Witch told me that those closest to me have paid for my journey. I had no one closer to me than Subaru, so if there were two people close to me, they must be Subaru and that 'true twin' of mine. You told me you paid for a vampire to come here to save your best friend who shares my soul. That means you paid for me to come here. You call your best friend your twin star. That can't be coincidence. That boy shares my soul, he is me. You are my 'true twin'."
Kamui pulled himself free from Fuuma's grasp. He held up a hand and cut through his skin with his sharp fingernail, letting his blood flow free. "Subaru and I did live for a long time, because of our immortal blood. I promised a girl named Hokuto that I would keep her brother Subaru safe, and return him to her once he'd grown old and lived a long, long life. If I were to give my immortal blood to this Subaru, and this Kamui," he indicated the bodies, lying motionless beside them, "they will be birthed from the same blood; and in that way, will they not, from a certain point of view, be twins?"
When the two Fuuma's remained silent, Kamui stepped forward towards the two bodies. He first forced Subaru's mouth apart, letting a few drops of his blood fall into Subaru's mouth. Then he went to his past self and did the same for the boy.
"I was told that Fei Wong Reed is the true cause of my grief," Kamui said as the blood dripped from his wound, "but I know now that this is incorrect. Fei Wong Reed learned from us. We broke the first taboo. We are the cause of our own grief."
The wound on his hand closed quickly.
"It's done."
The doppelganger smiled. "Thank you. Now, as for my payment..."
Fuuma fumbled around in his pockets until he retrieved a small crystal ball. "The payment should be extracted with this. Just put your hand on it."
The doppelganger inclined his head and obeyed. He took the still unconscious Kamui's hand and placed it on the ball, then placed his own hand over the newly made vampire's. The crystal ball flashed blindingly, and suddenly, a magical circle appeared underneath them, glowing with a bright blue light. Energy hummed all around them.
Then, without warning, a dimensional portal opened, swallowing the doppelganger and the newly created twin vampires. Before Kamui could run after them, the portal closed in a swirl of magic.
The energy enveloping them was absorbed into the crystal ball, which continued the glow softly, now a muted pink. When the last of the energy was gone, the ball fell, descending from Tokyo Tower at an alarming speed.
Fuuma cursed and jumped after the ball. Kamui quickly followed the hunter. In the last second before they hit the ground, Fuuma caught the crystal ball and summoned a dimensional portal of his own. He and Kamui fell into the opening, disappearing from Tokyo once more.
When they finally arrived at their next destination, it was at the Dimensional Witch's shop.
TBC...