Six drabbles, just like the title says. Rukia-centric, gen with strong Renji/Rukia undertones.
If she'd stayed
"Wake up, little sister."
Rukia rolled over. "'S too early," she mumbled.
"Come on. It's a present for you. For your birthday."
Rukia sat up, rubbing her eyes. "What's that smell?"
Her sister smiled. "It's bread. You put it in your mouth, chew it, and swallow it, and then you won't be hungry anymore."
Rukia looked at it dubiously. "Are you sure?"
"Very sure. Just try it."
Rukia took a piece and put it into her mouth. "Oh!" She took another piece, and another. "T'ank you ver' much."
"You can have the entire basket," Hisana said. "Happy birthday, little sister."
If they had never become shinigami
"A round of drinks on the house! It's my woman's birthday today!"
"Don't call me your woman!" A flying kick drove Abarai's face into the floor. The regulars started making bets.
People say they've been here since they were kids, which I can almost believe. Between Abarai's limp and Rukia's persistent cough, Rukongai has used them hard. Even so, they run the best sake shop in Inuzuri, serving drinks and booting troublemakers with equal efficiency.
"Bankruptcy? Is that my gift?"
"Sheesh, lighten up, Ruki-oof!" Money changed hands. I sipped my drink. Wherever they'd come from, their sake was /superb/...
If he had lived
"Happy birthday, Kuchiki!"
"You idiot, you'll drop the cake!"
Rukia blinked. "I don't know why you do this every year."
"You deserve it, Kuchiki. I mean, tomorrow you'll be locked away in that stuffy old house."
"Yeah, Kuchiki, you should spend your birthday with us, not your stodgy brother."
Rukia leveled her best icy glare at everyone in the room. "Do not speak of my noble brother in that manner."
The officers all paused for a moment and stared at her. Then, as one, they burst into laughter.
Rukia scowled. "You're all hopeless."
Kaien ruffled her hair. "Happy birthday, squirt."
If she'd stayed in the mortal world
Rukia's birthday was the day she finally came to terms with the fact that her powers were completely gone, and weren't likely to return.
That afternoon, she sat by the canal and took an honest look at her situation. Though she was long overdue to return to Soul Society, neither her brother nor her division had come looking for her. She hadn't been able to fight a Hollow for months.
She'd simply have to get used to being human. Rukia stood, turned, and saw--
"You know, you're looking at a serious sentence," he said. "Time to go home, Rukia."
If he hadn't come in time
There are now two shrines in Kuchiki Byakuya's house.
The first shrine he visits every week. He often speaks to her, though not so loudly that the servants can hear, and he always leaves looking sad and resigned, yet content.
The second shrine is only visited twice a year, once on her day of birth and again on the day she died. When the servants pass by, they can hear only these words, repeated again and again:
But there is never any response. And so twice a year he leaves, always looking older and more haggard than before.
If they make it that far
Renji sank down beside her in their makeshift shelter. He looked as tired as Rukia felt-they'd been running and fighting nonstop for days. "I didn't get you anything."
"Anything for what?"
"You forgot what day it is, didn't you? January 14th. Your birthday."
"Hmph. When was the last time we got each other anything?"
"I'll get you something next year, I promise."
Rukia closed her eyes. "Do you really think we'll live that long?"
"We will," he insisted. "And I'll get you something nice."
Rukia couldn't help but smile. She let herself lean against his arm. "I'd like that."