So, this is a crossover that just simply needed to happen. Lotsa spoilers for Cardcaptor Sakura (anime or manga), none for anything else. I'm calling this a crossover with xxxHolic, but you could also read it as a cross with Tsubasa Reservoir Chronicle if you wanted. In the end, they're all the same. Which is one of the things I love best about Clamp.

Enjoy!

Come in.

Twelve-year-old Kinomoto Touya stared through the fence at the elegant house flanked by blossoming cherry trees. The school trip had brought the class to this part of Tokyo to visit a nearby museum, but Touya had felt the call well before the bus had even stopped. Though quite tall for his age, no one had noticed the dark-haired, serious boy slip from the crowd and strike out into the streets alone.

Touya could see more than just the house and its gardens. He could see the heavy barrier that defended it from spirits, and more than a few protections within as well. The whole area felt ominously like the air just before a thunderstorm - thick and too still and stifling. Crowds of spirits and ghosts hovered around him, but Touya held them back with a force of will that never so much as trembled. It was the sort of place he would usually avoid, though, for there were some things even he couldn't fight, not yet.

Come in.

But he had been called.

Touya stepped through the barrier.

He walked without slowing or stopping until he had reached the front porch, but paused at the door. It, however, opened before him of its own accord. Touya could see the polished floor and the hallway divided by screens beyond, but what he could not see and could not ignore was the inherent power in every inch of everything connected to the place.

"Very well," came a warm feminine voice. "If you will come no further, I can respect your caution."

A tall woman with flowing black hair appeared in a long, elegant kimono. She moved towards Touya, never taking her own intent gaze from his.

"Hello," she greeted him.

"Hello." Touya drew himself up tall and felt as though he dared not breathe lest he take in whatever was so pervasive here. "You called me."

"Yes, I did. You have great magic, child. You will hear others than myself and be drawn to them as well if you are not careful. But you already know this."

He nodded.

"Very well. My name is Yuuko. And I have a proposition for you."

Touya waited. He dreaded giving the woman even the slightest advantage.

"Normally, those who find their way to my shop come with a wish in their hearts. I can grant their wishes, but only in exchange for something of equal value. However, in this case, I would ask you to allow me to reverse this bargain."

"Reverse?" Touya asked.

"I have a task that only you can undertake, but it may cause you pain. In return, when this task has been completed, I will owe you a wish of similar measure in balance."

"I don't wish for anything," Touya said carefully.

"Perhaps that is true for now. But then, it is not a coincidence that you have come here today. There is no such thing as coincidence in this world; there is only necessity. It is necessary for this task to be completed, and you will be grateful for it when someday you do find a wish in your heart."

Touya let out a slow breath. "What is this task?"

Yuuko produced a small item from the broad sleeves of her kimono. "You must take this home with you, but never open it nor speak of it. You must ensure it remains in the possession of your family until the correct time."

Touya's natural instincts and his gift of foresight served him well and all at once he understood something Yuuko was not saying. "It's not for me. It's for my little sister."

Yuuko smiled a tiny, knowing smile. "My, you are quite powerful."

Touya's will hardened and he made a fist. "I won't let anything happen to Sakura!"

Yuuko's smile widened and grew predatory. "There are some things even you cannot prevent. And there are other things that should not be prevented. Your sister's part is defined by fate. You cannot protect her from necessity. Rather, you would do well to accept my bargain so that if you need help someday, I will be bound to give it."

Touya warred within himself. He wanted to run and never look back, to go home and tuck little five-year-old Sakura safely against his side and never think of this strange woman again. He wanted everything to be all right. But he could feel the chains of something weaving around him and he thought they might be the fate Yuuko meant.

"Will it hurt her?" he demanded.

Yuuko's face fell. "Even I do not know all things, child. But I choose to believe in her. She is the one who is needed and the one who has been chosen. She is the one trusted by someone I would trust above everything. If this hurts her, she will be stronger for it in the end."

Then she held the item out. "Here. Feel for yourself. What is here may cause her trouble, but it may also protect her more than you ever could when the time is right."

Touya accepted the red and gold book with the beast on the cover and could feel the powerful, profound magic sweep through him. He could taste the very nature of Light and Dark, could feel the Elements hum, could sense a world of power and delicate control bound up together. He did not know what the book portended, nor what precisely it would do. But he knew that it would open for him if he willed it to, and he knew also that it was wrong to do so.

"You see?" Yuuko said. "It is already hers. Carry it to her and keep it for her. And someday return and we will fulfill our bargain."

Touya looked up at the woman again and realized she was bound by the same chains that bound him, that bound this book, that bound Sakura.

Touya held the Book of The Clow against his chest and nodded.

-==OOO==-

That night, Touya slipped the book in with the fairy tales and legends in his father's library. It was a section Sakura was not yet tall enough to reach without help and one their father would not peruse on his own.

Before turning away, Touya informed the book, "I know what you are. Take care of Sakura."

-==OOO==-

A few years later, the Kinomoto family moved to Tomoeda. No one noticed when Touya made sure to pack and unpack one particular box, setting the Book of The Clow on a lower shelf this time, though not quite so low Sakura would find it just yet.

-==OOO==-

Some time after that, Touya felt a surge of power from the Book. The next day, a new student joined his class named Tsukishiro Yukito. And Touya knew at once that this boy was connected to the Book and he also decided he didn't care. Whatever Yukito was - and he was clearly something other than he appeared - he was special and Touya intended to protect him just as he had always protected Sakura.

-==OOO==-

The spring of Sakura's fourth grade year, Touya came home one night and felt that the house was no longer the same. Fear in his heart, he pounded down the basement stairs and looked to where the Book had resided for so long.

It was gone.

Touya's fury grew, though he kept it silent. It wasn't time yet! Sakura was too young, and her magic was not as strong at her age as Touya's had been then. She wasn't ready!

But he knew. And he could not stop the fate that awaited her no matter how he tried.

He could only guard her and watch over her more carefully than ever.

-==OOO==-

Touya witnessed the Final Judgement from the ground, only Kaho ever knowing he was there. Touya had rarely been farther than that from Sakura throughout the entire ordeal. And he would never be farther in the future, either. Not from Sakura and not from Yukito, no matter what fate held for them both.

-==OOO==-

And when Touya finally sacrificed his powers to Yue once and for all to preserve Yue and Yukito both, he understood the necessity of the bargain with Yuuko. He understood at last that she had known all along the wish he would make at her shop one day.

But Touya chose to wait.

-==OOO==-

He did not return to Yuuko until several years had passed and Sakura's magic had grown strong and true. He did not dare go until he was absolutely certain that Sakura had more than enough power to sustain Yue on her own. He explained his intent to Yukito and Yue and waited until they were prepared to return to drawing their strength from Sakura directly, and then he waited another month just in case.

Only then did he catch a train one bright day to the shop hidden amidst the streets of Tokyo.

This time, if he had not known where to look and how to look, he would have seen only a wisp of smoke rising from an empty lot between buildings. Without magic he could no longer perceive the barrier nor what it concealed nor what it defended against. But he carried his wish in his heart as well as the unfulfilled bargain and it was enough. The house flickered into sight just as he crossed the threshold into the front garden.

"Welcome back," Yuuko said, standing before her porch this time. "You have grown."

Touya dipped his head slightly in acknowledgement. "I have come to complete our bargain," he said.

"Oh? And what is it you wish of me?" She smiled lazily. Of course she already knew. She had known from the instant she passed Clow Reed's Book into the hands of a blood-sibling to the one fated to become Mistress of the Cards.

"Restore my power. Sakura can sustain Yue now, and they will not be harmed by the transfer. Return to me what I gave up."

"May I ask why you want it back?"

Touya frowned but answered: "Because even if she is a thousand times stronger than I, even if her magic surpasses mine by so much, Sakura still needs someone to protect her."

"She has guardians for that."

"And she has me," Touya said firmly. "She will always have me."

Yuuko's lazy expression faded and she looked almost pleased. "Very well. The knot you have tied to hold your sister tight is strong enough, and I do owe you a wish for your service to me."

Yuuko spread her arms and a magic circle formed on the ground beneath Touya's feet. There was a rush of sound and sensation that ended almost as quickly as it had begun. But what it left behind was anything but momentary. Touya felt as though his skin no longer fit correctly, as though he had grown in dimensions other than the body. Then everything shifted and felt right.

Touya lifted his eyes and saw Yuuko properly. "Thank you." He bowed to her.

"Never mind. Our debt is now paid, unless you have another wish?" Her face crinkled impishly.

"No, but I appreciate the offer," Touya said. "I will not see you again."

He turned to leave and did not need to look back to be certain that Yuuko was nodding. They both knew it, after all. Fate had been fulfilled and Kinomoto Touya had no further need of the powers of the Dimensional Witch.

Though he fully intended to ask Yue about Yuuko and her connection to Clow Reed at the next opportunity. Just in case.

After all, anything with chains that strong to Clow Reed must be connected to Yue and therefore to Yukito and Sakura. And Touya would not fail to protect them even from fate itself if necessary. He would do anything necessary to protect the ones he loved.

And that, of course, is why Yuuko called him in the first place.

There is no such thing as coincidence in this world; there is only necessity.