Alluka has only known company.
Has only ever understood the prospect of sharing space; of sharing hands and tongues and thoughts and being full, but not quite. They've never been alone, they've always had Nanika. Even during the days the world was barred from them, both of them, with flowers painted on the walls and toys crunched against the corners like forgotten papers. Nanika was there - white skin and bouncing feet all the same.
When Nanika cried, they felt it. Felt the ribs quaking, the hunched spine as she fell, hands clutched around her mouth and stomach; even at age seven, trying not to disturb the family beyond the steel room. And every time, Alluka would wrap their arms around themselves, feeling the chubby fingers almost cross over their shoulder blades and they'd hug their sister back to her feet. Until this seven year old, with the broken heart and the face that only showed when Alluka asked for it, requested for it, was smiling again.
But Alluka had also known loneliness.
Had known it when Nanika slept in their knee bones, napped against their collar bones and Alluka had woken. There was an emptiness in their chest, even if they knew their sister was still in there, crumpled against the base of their shared heart. And they understood - knew that because their family had never felt this feeling of company, they couldn't be blamed for locking their children away.
Still, it didn't quench that bird-blown loneliness in their chest that felt like a dug-out crater at night.
But Killua, sweet Killua with the ice in his eyes and the sun in his hands, had known loneliness. He'd always had that sadness in his chest, thrumming like a guitar as he walked, but he'd never spared any of that ice for Alluka and their sister. He'd only treated them to the warmth of the sun, the beat of it in every hug and smile he gave them both. Alluka knew where that sadness had come from, how it had been bred from under their mother's nails and the back's of their father's teeth. They'd been spared that fate, that torture, for steel walls instead.
And Alluka was surprised, when their brother came back through those doors and collected them into his arms like a bunch of fallen leaves, that the ice was gone, had melted in some far-away sun on his adventures. They hadn't commented, had only played with him until Nanika had appeared to greet him and they made their way down the mountain, dodging Tsubone and Gotoh and Canary.
Even on the airship, as he buckled them in and kissed their head, they didn't comment on the way his smile grew with hope, with relief that filled his shoulders like bounding breath. Only felt Nanika wiggle her toes beneath theirs, ghost appendages moving the slippers that he'd given them.
They'd slept after that, and Nanika had awoken. Had placed her hand on a shriveled arm, and in the dead of night later, Nanika would tell Alluka how their brother had cried; their brave big brother with the electricity in his bones and the wild Savannah in his teeth had begged to save this person beneath the sheets. Alluka could feel their heart shrivel and swell all at once, and Nanika held them, hugged their sibling until they came back to the real world.
They wouldn't meet the person beneath the bed sheets until a few days later, when Killua's mouth split into a hurricane of yelling and flinging his arms around, so much that Alluka jumped when a pile of blackened spikes and green jackets came throwing themselves on their brother. They'd screeched, and Nanika had laughed loud in their gullet.
A few bouts of yelling and laughter had filled the busy street as the two boys met and suddenly the blackened spikes peered up from under Killua's arm and - there. The sunlight that had melted the ice in their big, big brother's heart.
"Alluka!" he'd yelled and had bounced forwards, plunging his arms around their shoulders with a grin and had pressed his head into their hair. They'd frozen, arms straight in place and eyes wide until slowly, with more mechanical screws in place than any seven year old had any right to have, tucked their own around his, this boy splitting with sunlight. This familiar face.
He'd pulled back, staring into their round features with a grin that could put a supernova to shame. And he rubbed his hands up their arms, warming them back into the world. "And Nanika too, if you're there. It's nice to meet you two; Killua talks about you guys so much. I'm Gon!"
They both hadn't started to cry until that. The sun in Gon's features had immediately dimmed and he'd tripped over his words, rocks in his mouth as he tried to apologize to all three Zoldyck children, with Killua yelling about what've you done now and Gon shaking his hands saying t-they just burst into tears!
Alluka can feel their sister laugh through her own tears, and to show that Nanika is listening to this boy, the boy that melted their too-strong big brother and had been one of the first to say hi to Nanika in a long time, smiled through her own tears. They lifted a chubby fist, wiping away the fat tears that escaped with a breathy laugh. "Nanika...Nanika says it's nice to meet you too, Gon."
There'd been a pause, and in that time, Killua had grabbed their hand and shrugged towards the towering body of the world tree in the distance and Gon had launched into a tale of what they'd missed. How he'd talked to Ging and Leorio had ran from the stage to catch him and -
Alluka can feel Nanika laugh, can feel the loose grip of Killua's hand and they know, they'll meet Killua's friends and they'll probably say hi to Nanika too and this feeling of fullness, not just company, in Alluka's chest is something they'll hopefully get used too. Will see these familiar faces and know, they're the reason her brother's hand is warm and this boy, with the sunflowers in his throat, made Nanika feel real for once.
For that, Alluka is thankful.