Author's Note: I never watched the zanpakutou arc of the anime, so if anything in my story contradicts with the anime, please excuse it.
Disclaimer: I own the fingers that typed this story. Everything else belongs to Kubo Tite.
Summary: Sode No Shirayuki muses about Rukia and their partnership. Dark.
Sode No Shirayuki watches her. Partnerships are complicated. There are rules, unspoken agreements. It's hard to respect someone's privacy when you yourself are but a facet of the other's soul. Things slip through, become known. Even when it is not the intent, a secret may be shared. Accidents happen.
Even so, there are other agreements. They are aware of the imperfection of their shared power, of the true nature of their bond. Sode No Shirayuki is part of her. And yet she is herself. She watches Rukia, and it is from the vantage of a detached observer. She watches the turmoil in their shared soul. Not really shared. How do you share yourself with a part of your own existence?
They do not speak of the things that slip through from one to the other. Mostly it is Rukia's secrets, Rukia's problems, Rukia's thoughts, that cross the demarcation in their soul. Her soul. And they do not speak of them. This is how they have always worked.
Sode No Shirayuki keeps her attention focused on her world. The icy barrenness of it is lonely at times. The moon is always full here. Full and round and ripe. Day never really breaks in this wilderness. The time is passed between darkness and a period of half-light, a mixture between dawn and dusk. And the blackness steals to the sky again.
Sode No Shirayuki had never experienced anything else. The glimpses she unintentionally gleaned from Rukia were fantastic, impossible. She could not fathom the existence of anything other than the cold, sparkling tundra and shimmering moon. That there was another light-one that could bring warmth and life-was beyond her.
Sode No Shirayuki had no way of reckoning the passage of time. The "dawns" do not come at regular intervals. They are random, unpredictable. She doesn't know what triggers the lightening of the sky-only that it has something to do with Rukia.
The loneliness is complete. Rukia knows of her presence, but they do not interact as Sode No Shirayuki feels they could. The loneliness is chased away when Rukia draws on her strength in battle. The Shinigami calls her, declares her name with confidence, and Sode No Shirayuki is ripped from the frozen world. Her form is different. Here she is long and thin. She tapers to a precise, sharpened point. Her pure white appearance is dazzling, beautiful. She is almost too beautiful for the grisly work she is called to do.
Sode No Shirayuki lends Rukia her power. It is her purpose for existing. And what a sad existence it is. She is friendless, bereft. But she has a name. To be nameless would be agony beyond description.
At least Rukia acknowledges her existence, even if it is only because she is valued for her deadly grace, her raw power. Perhaps if she waits long enough, things will change. Each time Rukia calls for her help, she gives it willingly. She was born for this.
Eventually, Rukia asks her for more power. Sode No Shirayuki divulges the secrets of her gifts, names the attacks that Rukia can command from her.
First Dance, White Moon.
Second Dance, White Ripple.
Third Dance, White Sword.
Their abilities grow. Sode No Shirayuki fights alongside Rukia with increasing frequency. At one point, it seems to her that she has spent more time in the physical world than she had surrounded by the landscape of Rukia's soul. And they become partners. Their bond goes deep.
Glimpses of Rukia's world become more frequent. She learns to interpret the state of the world around her with the fluctuation of Rukia's mood. Blizzards rage when the shinigami is troubled. The turmoil of the inner world betrays her anguish. There was a blizzard the day that Sode no Shirayuki found herself turned upon a human form.
Rukia was cutting down her mentor.
Sode no Shirayuki stood against the driving snow, unprotected. She was defenseless. The white expanse offered her nowhere to hide from the violent storm. She screamed at Rukia, screamed herself hoarse, but her voice was lost in the howling wind.
When the temperature dropped to the point that the breath puffing out of Sode no Shirayuki's mouth turned to ice crystals almost instantaneously, she knew that rage had overcome the petite woman. And whenever darkness fell upon the snowy world, Sode no Shirayuki felt Rukia's fear. Determination sent a steady, bone-chilling wind sweeping over the snow-covered tundra.
And still, Sode no Shirayuki weathered the elements alone. She wandered the endless plane, and the great eye of the moon watched her impassively. She had grown to love the moon and it's soft, silvery light. Once, Rukia's depression and self-deprecation had been so severe that the moon had simply disappeared. Sode no Shirayuki was plunged into a deep darkness that pressed in on her from all sides. The darkness was heavy, suffocating.
Rukia was harder to reach than ever. No matter how loudly she screamed, there was no answer from the Shinigami. And she suffered the crushing darkness alone.
Sode no Shirayuki slipped into herself. The darkness smothered her, pressed on her relentlessly. She could feel herself slowly fading away, fading into the blackness that surrounded her. She ached to be summoned out of this torture, to dance with Rukia in the leap and lunge of battle.
The darkness became heavier. Sometimes it lifted briefly, when Rukia's depression eased. Sode no Shirayuki drew in deep lungfuls of biting, cold air. The moon glowed dimly on the pale snow. It was never long before the darkness crept back in though. Hopelessness, despair. Anguish. Sode no Shirayuki's being cried out, seeking relief from the inescapable blindness. Where was the moon?
It had to be here still. Beneath Sode no Shirayuki's prostrate form, the roughness of the frozen tundra chafed at her skin. The moon was still there. It just wasn't strong enough to pierce the darkness cloaking the inner world.
What was stronger than the moon?
If it had been an enemy, Sode no Shirayuki would have cut it down. If it had been a hollow trying to devour her soul, Sode no Shirayuki would have sliced through it. If it had been anything but Rukia herself, Sode no Shirayuki could have saved them both.
What was brighter than the moon?
The moon only reflected light. It could not shine on its own. So what was it that the moon drew its strength from? Sode no Shirayuki had no answer. If she could find that source, find that which gave the moon it's light, surely that would be strong enough to dispel the darkness, right? If the magnificent, vibrant moon did not create it's own light, where did the light come from?
It was beyond her to fathom something more magnificent and vibrant than the moon. What would you call something that powerful? How could such a thing exist? The moon pulled the tides, outshone the stars.
What could outshine the moon?
Sode no Shirayuki got her answer. The answer came in a dazzling light that shattered the darkness. The spears of light pierced through it as through smoke. The darkness dissipated, unable to withstand the focused intensity of the light. The golden glow fell upon her skin, warming it.
A dark figure towered above her. Behind it, a bright disc had banished the night. The sky shone a soft blue she had never seen before, and the moon had faded to a mere ghost's image of its previous glory. It was nothing to look at now, with something far brighter, and fiercer dominating the sky.
The dark figure emanated power like the disc it had brought with him. He was Zangetsu. The Black Sun. And he outshone the moon.