Disclaimer: I don't own Shingeki No Kyojin, it belongs to Isayama Hajime.

Author's Note: Hey there! To be honest with you guys, I shouldn't be uploading another fanfiction, but I couldn't resist this idea. To be sure, no Mikannie in this fanfiction, just Aruannie, Eremika and maybe other couples.

Well, I hope you enjoy this first chapter, and please read the continuation of the Author's Note at the end!

Chapter 1: A Promise They Might Regret

Going to bars with his best friend was something Armin Arlert seldom did. It's not that he didn't enjoy Eren's company or drinking, it's just simply he wasn't comfortable with the environment. Besides, almost every time he went with Eren to The Wings, he'd always have to drag his very drunk friend back to their dorm, and then deal with him until Eren sobered up. However tonight wasn't like most nights, and he was more than happy to be with his friend and tell him all about the joyous event that took place that same evening.

"About damn time, Armin!" Eren said after hearing Armin's tale. "I was really thinking you'd never man up, and ask her out! Though I'll admit that to ask Annie Leonhardt out of all people, you need balls of steel! Way to go, dude!"

Armin smiled sheepishly at his friend. It hadn't been as hard as Eren made it sound. The problem had been overcoming his own insecurities, and finally telling Annie he had been in love with her since the ninth grade. Of course, he didn't tell her before being at least 50% sure Annie liked him in more than in a friendly way; and to his never-ending surprise, she was in love with him as much as he was with her. It was a very happy event, indeed.

"You… you don't mind, right Eren?" After some seconds of silence, Armin decided to speak.

Eren Jaeger looked at his friend in confusion. "Huh? What are you talking about, Armin? Why would I mind?"

Armin sighed, and shook his head. Eren was as clueless as ever. "Didn't you like Annie too?" He dared ask, and to his amusement, Eren spitted his beer and started choking.

"Where did you hear that? Did Jean tell you? Because if he did, I'm gonna beat his horse ass into−"

Armin just laughed, before saying, "Jean didn't tell me anything. It just seemed to me that you like her, or at the very least, used to like her at some point."

Eren sighed. "You and your damn perception skills! Fine! I'll tell you the truth: I used to like her when we were like fifteen, but I've been long over her since. Don't need to worry about that, she's all yours, man!" Eren said, patting Armin's back, causing the latter to laugh once again. "Just promise me you won't tell Mikasa."

Armin rolled his eyes. "You don't need to worry about that. Mikasa already knows, hardly anyone in our school didn't know."

Eren looked at his best friend with a horrified expression. "Fuck. Mikasa's going to kill me!"

Armin snorted. Ever since Eren and Mikasa had kissed at Jean's birthday party, things had been very awkward between his two best friends. Mikasa had always been in love with Eren, practically since the moment they met, but it took Eren twelve long years to think that maybe he didn't see his best friend as just a sister like he had initially thought. Honestly, Armin was starting to think that Eren would never realize his feelings on his own.

"I doubt she'll kill you for liking someone when you were fifteen." Armin replied, causing Eren to smile in relief. "But you seriously need to talk to her, and clear out whatever's happening between you both." He added, causing his best friend's smile to disappear.

"I know! But I don't know what to say to her, or how to act around her anymore! What if it was just a spur of the moment thing?! Or what if we date, and then we fight and break up, and our friendship is ruined forever?! Or what if she doesn't feel the same?! Oh God! She doesn't! She hates me! Shit!"

"Eren, for heaven's sake, stop panicking!" Armin said, hitting his friend on his head. "You're overreacting."

"Thanks, I needed that…" Eren said, nursing his abused head.

"Though, if you really want to know how Mikasa feels, just talk to her."

"Fine. I'll do it." Eren said, slightly annoyed at Armin. God, why was he always right?

"Speaking of Mikasa, do you think you could tell her Annie's my girlfriend now?" Armin asked, and in an instant Eren froze.

"Hell no."

"But Eren−"

"You really wish to see me dead, don't you? You know how Mikasa is whenever anyone mentions Annie, and I doubt she'll be excited when she hears you're dating her." Eren said matter-of-factly.

Armin sighed. "You're right, but she needs to know."

"Yeah, although she's not gonna be too thrilled about it, and I'll be surprised if Mikasa doesn't try to kill Annie for taking you away from us."

Now it was Armin's turn to look horrified. "She wouldn't, would she?"

"Never underestimate Mikasa, or Annie for that matter. It's the worst thing you can do, trust me." Eren answered, remembering all those times he was at the receiving end of Mikasa's and Annie's wrath. He shuddered at the memories.

"Crap! What am I gonna do? They will have to see each other on every birthday, party or reunion we have! We can't have them fighting all the time! I don't wanna see either of them getting hurt!" Armin exclaimed, terrified at the prospect of having his girlfriend and best friend going at each other every time they meet.

"Yeah, but what are we gonna do? It's not like we can force them to get along or anything, right?" Eren joked, but Armin had stopped listening to him, his mind working on a plan that was sure to function.

"That's it, Eren! They will have to try and get along!" Armin said with glee on his eyes, totally missing Eren's shocked face.

"You're not serious, are you?"

"Of course I am! It's the only way! If this is going to work, they will have to promise to stop fighting and try to get along. Who knows, maybe they'll even become friends!" Armin said in a hopeful voice, unaware of how terrified Eren looked.

"Armin, are you fucking nuts?!" Eren exclaimed, wondering if maybe his friend had drunk too much beer.

"I'm not mad! I think this may actually work!"

"Oh yeah? How?!" Eren asked him.

"If I tell them I want them to get along for my sake, I think they will do it. After all, both of them love me." Armin said quite confidently, smirking at Eren.

Eren merely chuckled and said, "You're a manipulative little bastard, did you know that?"

"So I've been told."

"Fine. I'll help you. But if this doesn't work, don't tell me I didn't warn you!"

Armin smiled in victory. "So, this is the plan…"

"No."

"But Mikasa−"

"I said no, Eren."

The young man sighed. This is exactly how he thought things would go when he told Mikasa about Armin's wish. She had been upset about the news of Armin dating her arch nemesis, but when she heard Armin wanted her to befriend Annie, shit went down the hill. Mikasa had refused to listen to Armin's reasons for wanting such a thing, and she didn't soften one bit when he told her to at least do it for him. Eren wanted to smack himself and Armin for coming up with such an absurd plan. At last, Eren thought he might convince her if he used guilt as his weapon.

"Fine! I guess Armin will be very unhappy when he watches you fighting with his girlfriend, and ruining every reunion he hosts. And, eventually, he will get tired of it all, and stop inviting you altogether. And of course I won't stay too long in his parties without you, and when we least know it, our long-lasting friendship with Armin will end, and all because you two couldn't get along."

Mikasa looked at him with a mortified expression, the sort of expression that on rare occasions appeared on Mikasa's face. Good. Eren thought. It seems this is working. He watched as Mikasa sighed, shook her head, and looked at him with an annoyed expression.

"Alright, I'll try to get along with her. But I can't promise it'll work." She finally said, and Eren looked at her victoriously.

"Good, because Armin wants us to go to the movies with him and Annie on Saturday."

At that moment only one word crossed Mikasa's mind. Fuck. Eren noticed her expression, and, sighing, wrapped his arms around her.

"It won't be so bad. I promise." He whispered, unaware of the fact that Mikasa's face was flushed a deep hue of red. "Plus, I'll be right next to you all evening!" He added, making Mikasa smile.

At least I get to be with Eren. She thought, trying to find a silver lighting to her current situation. Still, a little voice inside her head told her things wouldn't be as easy as Eren tried to convince her they would.

"Are you shitting me?!" A totally pissed off Annie exclaimed.

So long for a nice evening with my girlfriend. Armin thought grimly.

"No, I am pretty serious, actually." Armin said, resisting the urge to cringe when Annie growled.

"You know I hate Ackerman, right?" Crossing her arms, Annie asked her boyfriend.

"Yes."

"You know we always fight?"

"Yeah…"

"And you know we can't be in each other's presence for more than ten minutes without wanting to rip our eyes out?"

"Ammm, yes?" Armin gulped and answered nervously. God was Annie difficult!

"Then why would you think it's a good idea to become friends with her?! Are you out of your fucking mind?!"

Annie screeched and Armin had to cover his ears. Oh God, what did I do? He thought grimly, thinking this might be the shortest relationship he'd ever had. However, he also knew that this subject needed to be addressed sooner or later, since it was of vital importance to him.

"Look Annie, I want to be with you, but I also want to keep my friendship with Mikasa, you know? We've been friends since we were nine, and I don't want to lose her or Eren. I don't want to lose you either, so I thought that you two could try and be friends, or at least try to get along, alright? I know it's too much to ask, but, I really want to be able to take you to any parties Eren or Mikasa host without worrying about you not getting along with Mikasa."

Armin's words calmed, and even warmed Annie. "You really want me to go with you to their parties?" She asked in a soft voice.

Bingo! "Of course, Annie! You're my girlfriend after all, aren't you?"

Armin's words were accompanied with the sweetest smile he could muster: Annie's one and only weakness.

Damnit! "Fine, I'll try to get along with her. Though I don't think it'll work."

"Thank you Annie, you're the best!"

In that moment, Annie knew she had made a big mistake, however, she could never say no to Armin.

On Saturday the four of them met in front of the cinema, prepared to see the Mockingjay movie. Annie and Mikasa glared at each other as always, while Eren and Armin watched in the sidelines, sweat-dropping. To ease the tension, Armin decided to speak:

"Hey, Eren and I are gonna get popcorn, you guys want anything?"

After both girls told them what they wanted, the guys went away, leaving them alone. Again the glaring started, both trying to measure up the other.

"Alright Ackerman, Armin told me we have to get along from now on." Annie spoke first.

"Yeah, I heard the same." Mikasa retorted, still glaring at the shorter girl.

"I'll try to tolerate your presence, but if you piss me off you're going down."

"And if you dare to hurt Armin, I won't hesitate to kill you."

"I'd like to see that happening."

The glaring continued until the guys arrived, who immediately noticed that the tension hadn't gone away. Since it was time for the movie, they decided to go in already, and the tension eased down a little bit. However, when the guys weren't looking, Annie and Mikasa turned to look at each other with the same look on their faces: It's on!

They would try to get along, yes, but that didn't mean they would stop hating each other. From now on, they would try to see who would break first, each hoping it was the other. No matter how much they loved Armin, they were already regretting the promise they made him.

A/N: Here are some points that need to be addressed:

1. I know that in America and other countries the legal drinking age is 21, but for the sake of this fanfiction, in the fictional country they live in, the legal drinking age is 18. So, they've been going to bars since 18, so Armin should be used to drunk Eren by now, lol.

2. Yeah, they're all 21, and are about to finish college.

3. I put Mockingjay since I just saw that movie hehe. I don't own the movie either.

4. Things like Jean's party will be addressed later.

5. The rating may change from T to M, I'm not sure though.

Anyways, I really hoped you enjoyed it, and I'll like you to give me your opinion about which degrees should they be majoring on. I thought that maybe Eren could be studying criminology, and Armin maybe anthropology, what do you guys think?

Again, I hope you guys liked it, and I'll see you soon!