Bucky had known since Wakanda.

It was the kind of knowledge that was confusing at best, because it made no actual fucking sense. The King's sister — that feisty little shit — was a genius. One by one, she undid Zola's dirty work, picking out the memories he lost during his tenure as Hydra's killing machine. Bucky was reduced to a pile of crying mess night after night, retching up the content of his stomach as faces of those he had brutally murdered swam behind his eyelids. T'Challa was understandably worried, because dude was a saint. The princess cackled at his misery and made a show of ostracising him to live in a mud-hut near the border, citing something about shooing the bad omen away, but he knew that she only did it to permit him privacy — so no one would see Bucky sob his heart out.

He remembered life before the war with Steve. He remembered the war. Bucky remembered all those times he spent out of cryo and on hydra's operating table, the cold cut of a knife against his skin, the metal of the Winter Soldier's arm shoved carelessly against his shoulder socket, everything. He remembered his encounter with the man on the bridge, and the confusion that arose with it because he knew that face, that voice, that gentleness — and the painful wipe that came after. Then Steve was there again, trying to pull his chopper down. And even though Bucky had tried to kill him over and over again, Steve almost smashed Stark's skull in, dropped his shield, left the Avengers, all of it only so he could have Bucky back by his side.

All of that made sense. The palace's library and T'Challa's private newspaper collection (Bucky still wasn't quite ready for the internet) also filled him in on what had been happening with Steve, prior to, and after his nosedive into the Arctic. Bucky plotted out their timelines in his head, and it all made sense. Or at least it did until Shuri dug deep for the last time and unearthed a memory of one encounter Bucky had in the 1950s (he didn't remember what year. Hell, he didn't even remember his own name back then). It was with the man on the bridge, and that seemed impossible, because Steve should have been in the ice and remained undiscovered for another few decades. Bucky was sure he was not hallucinating, so it didn't make sense at all.

It wasn't until war was coming to Wakanda — they were preparing for battle, and the kimoyo beads showed a hologram of that asshole Thanos waving around his infinity gauntlet — that Bucky was smashed in the face with the reality that time travel was a thing. It was only then that he understood what was about to come to pass, and what had already happened. Bucky finally knew why the man on the bri— Steve, was there that day in Kensington, London, back in the 1950s.

Realisation smashed him like a tonne of bricks. Bucky sat down started hyperventilating. T'Challa sat with him, trying to get Bucky to have a bite of his food, to share what was on his mind. But the King's effort went to no avail as Bucky outright refused. Shuri came in and threatened to coat his vibranium arm with W'Kabi's Rhinoceros's mating scent.

'You don't want me to do it', she warned, 'I put it on my brother's sandals once as a joke, the females nearly mauled His Royal Pantherness to death. So eat your Bast damn food and talk to me.'

Bucky choked out a teary laugh, his resolve of self-hatred crumbling under her watchful gaze.

'He chose her— he'll choose her…' he finally admitted, feeling weak, 'He'll leave me.'

It didn't take long for her to put two and two together. Because a moment later, Bucky heard a quiet mutter of 'Rogers, you son of a bitch.'

But before he could wallow in misery for much longer, war was upon them. Then the next moment, Steve was there, clasping Bucky in a tight embrace. Bucky opened his mouth, and shut it, he wasn't sure what he wanted to say to Steve, so he settled for a few meaningless smart-ass jabs. He was relieved to see Steve finally, and anxious to talk with him alone. But then all hell broke loose around them, and Bucky found himself separated from Steve again. He threw himself into the battle, dodging attacks and using a talking raccoon as rifle extension. Bucky had seen a lot of things, but this was the kind of batshit crazy that he was not prepared for.

It could have been hours, but then the battlefield fell silent. It wasn't the nice kind of quiet, however, and Bucky could feel trepidation course through his veins as he braced himself for the calm before the storm. He raced to find Steve. Steve was in sight. He called out to him. Steve turned. Then Bucky crumbled to dust.

Fuck.

Five years sped-by in the blink of an eye. Five years Steve spent living without him.

As soon as Bucky came to, there was yet another fucking war going on, and T'Challa was hauling him through a portal that led to a decimated patch of land. The Avengers' HQ was nothing but a burnt up crater, and alone in the middle of it, stood Steve. Bucky raced towards him. He didn't care anymore that they were in the middle of a fucking war even more hectic than the one before, he needed Steve, now.

So with all the grace of a semi-stable 100 year old man, he tackled Steve to the ground and bodily dragged him off to the side of wood.

'What the heck, Buck!'

'For one fucking moment, can you stop being Captain America?'

Steve quieted at that, seeing the seriousness etched into his features. Bucky wasn't going to stop now. It was now or never.

'Steve', he said vehemently, "You know this, right? You know that I fucking love you, you fucking punk.'

Steve seemed startled, and Bucky felt a lump in his throat.

'So I'll have you know that I'll be okay', he powered through, 'Wakanda's awesome. It's the shit. I'll be okay.'

'Bucky, what are you getting at—'

'All I'm trying to say is — don't worry about me', that's it, he could feel the tears coming. Fuck this shit, he was Sergeant James Buchanan Barnes, he did not cry, 'I'm gonna be fine, pal. So you… you do what you need to do.'

Steve quieted for a moment. Bucky wasn't sure if he quite understood the gravity of what he was trying to communicate then, but he opened his mouth and asked, 'Why are you telling me this?'

'Because I know you', Bucky said, 'Because you've risked your life, your reputation; Christ, you've risked plenty of other people's lives, you've killed people, you threw away everything just to save me. Hell, Steve, I— I know that you would spend everyday of your life, for the rest of your life, being unhappy, living other people's dreams, walking the path of their icon, if only it meant that I would be happy, that I would be safe. You would stay with me so that I would not be lonely.'

'Bucky—'

'Go', his voice was hollow. Bucky closed his eyes so that he would not have to look at Steve, 'Go chase your dreams. Go live your life. You've already done too much for the country, the world. For me. It's time you do something for yourself, Rogers. Be selfish, for once'.

Then in a rare moment of emotional display, Bucky tugged on the tattered string of a pocket watch he kept hidden away, and pressed the metallic device into Steve's hand.

'You'll not need that compass of yours anymore after this, punk', his voice broke, 'So take this. It's all I could salvage from Hydra. Keep it.'

Steve eyed him curiously, before snapping the broken pocket watch open. Inside was a picture of them back in the army days, with their arms around each other. Just the two of them without the other Howling Commandos. Bucky knew that Steve would not have remembered it, but to his surprise, Steve grinned and said, 'Stark was obnoxiously excited to try out his new camera that day.'

Bucky swallowed a lump that formed in his throat. He closed Steve's fingers around the pocket watch.

'You'll know when to find me. Go, Steve.'

Steve looked at him, truly looked at him, then a horrified glimmer tainted with hope lit up in his blue eyes.

'No… not without you', he said hoarsely, echoing Bucky's own words from all those years ago, finally catching on to what Bucky was implying. 'Buck… I can't—'

'I'll be fine', Bucky smiled sadly through his lie, 'I'm a lifetime ahead of you, pal.'

So he hugged Steve goodbye in the aftermath of the battle. He told him he'd missed him, told him he'd be taking all the stupid with him. And then he let Steve go. And for the first time since Bucky had known the man, Steve let go. He stepped onto that platform, and with one last look Bucky's way, disappeared from his life.

Bucky wanted to reach out, to hold Steve for one last time, to tell him how much he meant to Bucky, but Steve was gone.

Bucky held back his tears. He wanted to curl up on the ground and fade away, but he knew that with this new life that Steve had shed blood, sweat and tears to carve out for him, falling apart was not an option.

So he counted to five and looked towards the sunset, letting memories wash over him.

It was back in the 1950s, London, England. Bucky had been on a stakeout for five days, and he'd just completed his mission, assassinating someone important, most likely, he didn't want to dwell on who. He had been out of cryo for roughly a week, the mission had ended, and he was supposed to report back to Zola's team in 12 hours, but he was in a very bad way. He probably had at least 4 broken ribs and a sprained ankle, he hadn't slept at all that week, and hadn't eaten since probably 1949. Bucky was lying in a puddle of his own blood and sweat, somewhere in Kensington, when a man approached him. He didn't know who it was at the time, but he also didn't have any energy to fend off the blond man with the most beautiful blue eyes he'd ever seen, as he hauled Bucky up on his shoulders and carried him off. He slipped into unconsciousness shortly after, something which never happened to the Winter Soldier who was always on alert, but somehow, against all logic, Bucky felt safe in the man's arms, and he let himself be taken away.

When Bucky opened his eyes again, he was in a simple apartment somewhere in West London. Warm afternoon sunlight streamed through the one big window in the room, which was sparsely furnished, and probably costed more than everything Bucky ever owned combined. There was only the one single bed he was lying in, a night stand with a plate piling with roast beef sandwiches, and his Winter Soldier uniform washed and neatly folded at the foot of his bed. The Winter Soldier sat up and looked around the room; there were no signs of potential threats. Someone had also given him a proper bath and put him in comfy sweats and a t-shirt. So he ate his sandwiches, changed back into his uniform, grabbed his rifle, and slipped out of the window. He never saw the blue-eyed man again, or so the Winter Soldier thought.

Steve hadn't tried to change him then, hadn't tried to mess with his already messed up fate, but he saved Bucky in more ways than one that lazy afternoon in Kensington.

'It should have been yours', Sam said, gripping the shield awkwardly as he walked away from the man by the lake and towards Bucky, 'Dude, you were like, his other half', Sam floundered, 'Shouldn't this be yours?'

'I could never live up to his legacy', Bucky shrugged, his misty eyes trained on the figure sitting on the bench, 'Also, the world still hates me. Remember?'

'Naw, man', Sam shook his head and clapped Bucky on the shoulder, 'You just can't bear to walk the path that he has walked.'

'Maybe you're right.'

'Aren't you gonna go talk to him or something? Like, isn't that what best friends do after they don't see each other for, what— seventy years?'

Bucky wanted to scream, he wanted to be angry, he wanted to grab Steve by the shoulders and shake him — yell at him, ask why he bothered to bring Bucky back to life if he would have just left like that. Yes, it had been five god damn seconds for him, but Steve… Steve wanted him back, Steve did everything to get him back, and yet he chose to spend the rest of his life without Bucky. Why? What happened to I'm with you till the end of the line?

Instead he let his eyes follow the movements of the man on the bench, who slowly got up and ambled away, easily blending into the crowd perhaps for the first time in his long life, and sighed.

'Maybe some other day.'

And the day turned into a month, a month into a year, and in the summer of 2027, Bucky found himself staring at a dying man laid out in front of him in a soft cotton gown. Steve looked so frail, so impossibly old. Tubes were attached to his nostrils and arms, his strong arms that once wielded the mighty Mjolnir of Thor and held the iconic shield that safeguarded Earth now lay feebly by his sides. It was painful to watch him like this, and Bucky had to psych himself up. Yes, he'd seen a lot of people die, many at his own hand, countless with grim satisfaction. It was something else, however, to watch the love of his life draw his last few shaky breaths right in front of him with nothing he could do.

Bucky hated himself. He sat down on a chair next to Steve's bed and mussed up his hair.

"Hey, punk."

"Hey, jerk…"

The rim of his eyes were hot with tears that threatened to fall, but Bucky forced out a winning smile as Steve weakly took his hand.

"This remind you… of the old—" Steve coughed "…days?"

Bucky snorted.

"When we lived together in Brooklyn? You were so small and sickly. We barely had enough to get by, one pot of soup would last us three days. Now you're hooked up to all these expensive meds in this fancy-ass hospital and that's honestly what you think about?"

Steve gave the barest hint of a shrug, and another cough.

"It was the best… time."

"Then why did you leave?" Bucky's voice cracked. He dropped Steve's hand, "Why, Steve?"

"T-took all… the stupid with you to war", Steve rasped, trying to smile but failing, 'How… could I not have left to follow you?'

Bucky stilled. Steve knew that he meant leaving to find Carter in the past, but in that sentence, Steve clearly meant to tell him something else.

Steve's trembling hand nudged against his, and when Bucky looked down, lying there in his palm was the same old tattered pocket watch, looking a lot more worn now after seventy-years in the past. Bucky snapped it open, and there was a picture, albeit not the same picture that was glued to the lid the last time Bucky gave it to him. This one was even older… This was the one picture they had taken together in their old apartment in Brooklyn. Steve was still small and gangly, and he was hugging Bucky's waist, smiling brilliantly at the camera.

Bucky thought they'd lost it after the war began, but clearly Steve went back looking.

A lump formed in this throat.

"You know, Steve, I'd once thought — hoped", Bucky choked, "Hoped that you would have picked me." He bit back a sob, "And it was selfish of me, I know. I let you go, and you let go. And in those five seconds, I desperately wanted you back. Because after all that we've been through together, Steve? And You left? I've never lived a life without you since I could remember. And now — now… Now I'm the only one, Steve. A man out of time. Now I've got to spend the rest of my life without you."

Steve was still for a long time, so still that Bucky thought he had died. But then he spoke up.

'Maybe,' he rasped, 'In another lifetime…'

In another lifetime, where Steve wasn't Captain America and Bucky wasn't the Winter Soldier. In another lifetime, if he never met Peggy Carter, if the wars had never happened, if Red Skull never wreaked havoc, if Hydra never thrived. Maybe in another lifetime where none of this had ever taken place, and they were just two stupid kids who chose to never leave that crappy, old apartment in Brooklyn.

Maybe.

'It would have been you, Buck…' Steve slowly closed his eyes, his grip on Bucky's hand loosening, as his hand fell away from Bucky's for the last time.

Steve's voice sounded almost exactly how it used to.

'It would have been no one else but you.'