Uh there's a couple things I wanted to say before I get right into the story. First of all, the usual copyright stuff, I own nothing, blah blah. Second, I couldn't decide whether or not to have them use their human names or their countries names, so I went for a mix of the two. In case you're not familiar with it and you're too lazy to google -

Athur - England
Alfred - America
Ludwig - Germany
Ivan - Russia
Feliciano - Italy

In hindsight, it was really his own fault. He should learn to stay out of other people's business. If he hadn't been making all those jokes about England and France, none of this would have happened. Germany sighed as he remembered.

It had all begun at a world conference. Most of the countries took a while to leave, usually because they were gathering up their things, or talking to other nations, or in Greece's case, sleeping with a kitten perched on the top of his head, so even ten minutes after it was over, the room wasn't entirely empty. Germany was stood near the door, after having given up the hunt for Italy (who had vanished a little while before, making some excuse about needing to discuss sauce with Spain). He was absent mindedly watching France and Britain interact. America slumped against the wall next to him, munching on a ludicrously large hamburger.
"You know, you're an asshat, but god DAMN, you make good food." The bespectacled nation munched as he spoke, making his words all but unintelligible. Germany nodded and half-smiled at the backhanded compliment, not taking his eyes from the other two. Frowning slightly, America shuffled closer to Germany.
"What are you looking at?" He asked. Germany nodded towards them, as France moved forwards before Britain could stop him, and began brushing some imaginary lint from the lapels of Britain's suit jacket, purely for an excuse to touch the other nation. Britain allowed this for a second before pushing him back, and sweeping the front of his jacket with his own hands. Germany could just about hear Britain yelling at France and telling him to keep his hands to himself. Germany rolled his eyes at the sight, thinking the discomfort was all for show. America shot him a quizzical look.
"They aren't that interesting."
"They are. I think it's funny. They put so much effort into not being found out, when really, no one cares."
"What are you talking about?"
"England and France. They should just tell everyone they're screwing and have done with it all." Germany shrugged, as if it was fact that they were together, and not mere speculation of several nations. America's eyes widened as Germany spoke.
"You saw them fucking?!" He cried, clearly horrified at the prospect.
"Nein, nein. But don't you think it's obvious, what with the way they are around each other?" Germany looked back over to them, while America sighed with relief. France was smirking and leaning forwards, murmuring something that was undoubtedly an invitation to something illicit into England's ear, while England's eyes bulged, and he blushed like a schoolgirl.
"Nah, that's just France." America assured Germany, recalling occasions in which France had given Italy and Austria the same treatment. Germany chuckled and shook his head.
"It's more than that. I'm sure of it." Germany insisted, watching as France tugged Britain's tie off, tied it round his own neck and began to do a teasing impression of Britain, while Britain protested and grabbed for it. Finally, France relented, and replaced the tie. Holding one end in each hand, he flipped it like a skipping rope over Britain's head, and tugged on it to pull him closer. Britain found his body pinned against France's, and while he squirmed to get away, the other nation simply laughed. America scowled at the sight, but he didn't say anything; he was too busy thinking. He knew something Germany didn't, and he could easily use it against him if he played this right. It wasn't that he wanted anything from Germany, or felt he needed revenge for anything. He was just incredibly bored, and felt like having some fun.
"But... you have no proof?" He enquired, after a lengthy contemplation.
"Nein, I don't." Germany admitted. America gave him a little disappointed look, and he must have really known how to play Germany, because hell, if that look didn't bring out his competitive side.
"I have none now, but I bet I could find some." Ludwig couldn't help but boast. America shrugged, and nodded.
"Okay. And I bet you can't."
"Wait, are you betting that I can't because I'm not good at this stuff, or I can't because it doesn't exist?" Germany asked after a few moments of watching Britain smack France with his tie. America opened his mouth to answer, but then realised he wasn't actually sure.
"Look, let's write this down so we don't get confused." He went back over to the conference table, and found a piece of blank paper. Germany followed him, and sat in the chair next to the one America had claimed, while he searched for a writing implement.
"Hey Russia? Got a pen?" He gave up, and called across the room to the purple-eyed nation.
"Yes, why?" Russia began to glide towards them, his being enveloped in a mysterious glowing purple fog.
"It's nothing Russia." Germany said hastily, not wanting anyone else to get involved, should this go wrong. Not to mention that Russia creeped him out. America waved that off, and pulled a chair out for the other nation.
"Me and Ludwig here are making a bet." He laughed, taking the pen from Russia and beginning to write out some terms.
"Oh? What about?" Russia began to scan the document America was making. Germany groaned. He just had to ask.
"Welllll, Germany thinks that France and Britain are screwing," America nodded his head towards the other two nations, who were still pressed against each other, one laughing, the other trying to escape, "and I think they aren't."
"What are the stakes?" Russia asked. Germany and America looked at each other, having not previously discussed this.
"What do you reckon, Germany? Loser has to give up some land?"
"Aren't you a big enough country already?"
"Money then?"
"I'm really not that invested in whether or not they are screwing..."
"Well we need something to happen to the loser...What about a dare?" America suggested after a few moments of contemplation. Germany shrugged.
"What kind of dare?" He asked. America's eyes sparkled with glee as millions upon millions of bizarre and brilliant ideas popped into his head.
"The loser has to try and seduce China."
"Nein."
"Japan?"
"Nein."
"Russia's scary sister?"
"Nein! Und you do realise he is sat right next to you, don't you?"
"Yeah dude, of course I do. What about -"
"Can't you think of a dare that does not involve forcing yourself upon a potentially unwilling recipient, purely for the sake of the other's amusement?!" Germany demanded angrily. America seemed cowed for a second, before he snapped his fingers, grinning maniacally.
"What about if it wasn't unwilling?"
"Then it would be okay, I suppose. What are you thinking?"
"Whoever loses has to be a hooker for a week!"
"...Explain yourself."
"Well, it wouldn't piss anyone else off, and no one else would know, unless they happened to see whoever lost standing in a dark alley at night in a miniskirt." America shrugged, knowing it was a fairly weak argument, but keeping his hopes up as Germany hadn't immediately dismissed it. Germany ran through everything in his head. He was certain that France and Britain were at it, and in all honesty, he kind of wanted to see America in a mini skirt, and not just because he loved embarrassing him. Besides, if he lost, there'd be nothing to stop him just telling America to go fuck himself. He smirked, and nodded.
"Sure. I accept these terms." Germany nodded, and America scrawled them all down, as Russia watched.
"Now, you just have to seal the deal with blood." Russia insisted, smiling that creepy smile of his. Germany and America both turned to face him, alarmed looks on their faces. They both protested vehemently, but somehow or other, Russia managed to convince them to sign the paper with their blood, and allow him to cast some kind of enchantment over the whole affair.
"If the loser fails to cooperate with the terms, his soul will be forfeit to me." Russia chuckled, his being once again shrouded in a haze of glowing purple. Germany and America cast each other worried glances, wondering what the holy fuck just happened.

"So, how long do I have to gather this evidence?" Germany asked as he stood up.
"Uhh, an hour." America shrugged, having a rather short attention span, and not wanting to have to wait to claim his prize.
"An hour!? How do you expect either of us to gather sufficient evidence in that time?" Germany demanded. America just snickered, deciding that now would be a good time to reveal his secret.
"HEY BRITAIN!" America hollered over to the other nation, who seemed grateful for an excuse to move away from France. Germany sighed inwardly, expecting America to just straight up ask him if he was screwing France. Except he didn't. When Britain reached America's chair, America caught ahold of Britains wrist, pulled him into his lap, and captured Britains mouth with his own. Entirely unsurprised by this action, Britain responded with equal enthusiasm, wrapping his arms around America's neck, while Germany watched, open-mouthed.

After Germany pulled them apart, Arthur explained that he and "Alfie" had been shagging ever since the end of WWII, and that although Francis was obsessed with him, the feeling was not mutual. Germany snarled. He moved to strike America across the face, but Russia caught his arm.
"He wins." He said softly. Germany laughed harshly, shaking his head.
"That was not winning! That was cheating, surely?"
"No. The only rules states are that proof needed to be shown within the hour. And here is proof." Russia gestured to where Arthur was still sat in America's lap, watching the whole affair with an aura of amusement.
"Serves you right for gossiping, Ludwig." He laughed lightly, before turning to the contract. He laughed even harder when he saw what Germany had agreed to.