Sirius Black was used to being left behind.
It wasn't a whine or a complaint, just a fact. As a child, he had gone on a trip to Knockturn Alley with Mother only to be forgotten and retreived several hours later. He'd been forced to walk home alone one Christmas after starting a fight at his aunt's over the tie he wore to dinner. He was used to seeing the back of a head, to the sinking feeling in the pit of his stomach- over the years, it's developed into nothing more than numbness.
One day he found a solution to this problem; it was so simple yet had sat right in front of him for years without any acknowledgement. Why wait for others to do the leaving? Why not beat 'em to the punch line? And so he made a habit of it: being the first to leave the bed after being with a girl, the first to storm off from a fight, the first to end the relationship. Everything kept shifting from then on. A constant blur of pretty faces, hexes aimed at Syltherins, and screaming exchanges with the residents of the Most Ancient and Noble House of Black. Though the threats had started off as mostly empty- I'm leaving! I swear to God I'm leaving this hell hole!- the summer before sixth year was the embodiment of this new mentality. He was the one to pack up his bags, to step out the door and never come back. The look on Regulus' face was one he wouldn't forget; Sirius knows he'll never be forgiven for leaving.
It didn't bother him. To hell with the lot of them- the pureblood mania, the curses, the beatings- he was better off without them. It didn't bother him, he swore. But something had shifted in Sirius Black that summer. He felt it in him, the need to destroy everything looming, threatening to close in on him at any time. He did his best to keep it at bay; before doing anything, he'd ask himself whether or not someone would end up hurt. More often than not the answer was yes, but quite frankly he didn't care. It was never really a problem- until one day it was. When he surpassed the thinking process all together and nearly killed several of his classmates.
It was a mistake- a colossal, crisis inducing, extremley shitty mistake- but a mistake none-the-less. Not in James' eyes, though: for him it was the telltale sign of a pyscopath, reasons to kick a former best friend out of his house. I didn't mean it, I swear! I'd do anything to take it back! His family had more of a hold on Sirius than he'd ever admit. Years and years spent at Grimmauld place had proven as the breeding grounds of evil, infesting itself in the darkest crevises of Sirius' mind. It left him in the dead center of things- not good enough for his friends, but not quite fucked up enough for his parents.
Everyone has someone, Sirius reflected in his empty train compartment. Even Snivellus, who'd been accompanied by his parents on the platform- a frowning, cringing father, and a female Snape of a Mother. People who'd probably be very upset at the news of a dead son or one inflicted with lycanthropy. Not everyone's parents are yours, Sirius. Some actually do give two shits about their son.
Sirius Black was used to doing the leaving.
It's not as though anyone's tried to stop him.
.. And on that cheery note. Hello there readers, I hope you've liked this little angst-fest I call a one-shot. Poor Sirius with his poor abandonment issues. I'd give him a hug but alas, he's fictional.. and dead. Review if you liked it, or if you hated it, whatever tickles your fancy.