Spoilers: up to anime episode 016, right before the SS arc
Summary: Rukia, helping Ichigo adjust to her own powers, dwells in thoughts of Soul Society and makes a decision for his safety. (The poem is written by me.)

Sayonara


black as death, cold as ice, and –

See Rukia: in a flash she's the protector, promising souls eternal life without pain. In a poignant glance, she's seen reflecting on this scene of life and death atop a tree, her hat decked precariously on her sum-rimmed hair, eyes downcast and sullen.
She who has seen every nook and cranny of this world cannot bear to take another look.

See the blossoms dangle
From the trees of her soul;

Sakura petals skimmed the deep recesses of her mind; who was it she saw now, as her glance turned away from the human earth; who was the one she thought of? Lifeless creatures sighed for lesser things. She ached silently.

See the heart brutally attached,
Irresistibly promised in lies
And deceit.

She had to protect him from the laws of Soul Society. If all else they would follow her soon. Who was she to hurt these humans who longed to be free from sorrow? and why was she the one to be full-packed with it? but she decided, knew it to be true… This was no place for her; she had believed in its beauty, wonder, its ability to believe in others... how he saved lives because it hurt him so to see his family suffer. Indeed, he was the real hero; he had grown so much, but he would be alright. Wouldn't he? She wasn't attached here, no, she could leave him. And he wouldn't be found, wouldn't be hurt.

See the sword dipped in red;
the blue, the black, the white:

The sky lifted her away from her thoughts; the clouds crept lazily by, telling her she must not be so sad, nothing was ever so sad, and Rukia was determined now. She knew. Caught in the mixture of all these colors, she thought, and it must really be this black and white.

See those sitting in Soul Society,
an eternal sight.

Rain soaked her, almost drowned her, but she plunged on, running fast past the homes (she couldn't grasp their meaning, their comfort and joy).
She must leave.
For his sake.

Sayonara: in the light of the moon; I will always remember you; and please, if you will, remember me -- when the rain falls.