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Eren can't say he's happy with Armin's choice in boyfriends, but it's really hard to argue when he sees how happy the blond is when he meets up with Jean after practice, winding his arms around his neck to pull him in for a quick kiss. It's almost a little sickening, the looks they give each other, and he groans, slapping a hand over his eyes.
"Get a room, you two," he hisses as he walks by them on the way to the locker room, feeling rather smug when he catches the beet-red look Jean is sporting.
"Shut up Yaeger," the quarterback growls, pecking Armin one more time before following the rest of the team into the showers. The blond smiles, perching himself on one of the benches and occupying himself with his phone as he waits. It's a Friday afternoon and the season is just getting started. Coach Smith is insistent on winning championships again so they've started early. Early as in late spring. Krista is hosting a kick-off potluck at her house and the football team quickly breaks off into carpools. Eren opens his mouth to invite Armin into his customary shot-gun position in his silver sedan, but the blond has glued himself to Jean's side and he can't help feeling a little lonely.
He's not sure how to bring up the topic. He doesn't want to seem fussy or possessive. After all, he's just the childhood best friend who's been by his side ever since they were in diapers, who's fought off countless bullies and - Eren slowly unclenches his fists and takes a deep breath as he spoons some potato salad onto his plate. He finds a seat on the couch next to Reiner and they strike up a conversation when Armin slides in next to him, Jean in tow. They stare each other down over the blond's shoulder, with Eren doing his best horse impression. Armin pushes the two of them apart, huffing loudly as he jabs his elbows into their sides. "Play nice, you two."
---
"Armin's growing up," is all Mikasa has to offer, munching on a fry. Eren frowns, flicking a bit of lettuce at her, which she dodges smoothly. "Come on. Aren't you glad he's making friends?"
"More like making nasty," he grumbles, biting into his hamburger angrily. "I mean, it wouldn't have been so bad if it had been anybody else... Every time I see them, it's like they're trying to eat each other's faces."
Mikasa shrugs, taking his soda. "They're in their honeymoon phase. Don't worry, they'll get over it eventually."
"Jean calls him baby," he adds, a horrified expression on his face, but his sister ignores him in favour of stealing the rest of his fries. "And Armin likes it."
"If he likes it, then what's the problem?"
---
He watches the two of them discreetly from the other end of the food quart, Bertholdt sweating nervously at his side, looking terribly uncomfortable. "Hey. You're tall. Can you see what they're doing?"
"Uhm, er, well, I think... Armin's feeding him?"
Eren gags as he pushes back his seat and stands up for a better view, craning his neck. Armin is pressing a strawberry into the quarterback's mouth, giggling as the other nips at his fingertips. They're surrounded by shopping bags and the blond is practically straddling his lap as they share a kiss. "Are you kidding me? That's - no. Just no."
"Eren, what are you doing? Are you spying on Armin's date?"
"What? Mikasa?! No!"
He doesn't get it. Eren Yaeger is a good friend, one that looks out for the people in his life and makes sure they aren't being deflowered by long-faced idiots. Why can't anybody see that and appreciate it? He groans loudly as Mikasa hits him when he tries to intervene between the happy couple, currently window shopping as Jean slips his hand into Armin's back pocket and squeezes, grinning. Armin blushes, but he doesn't move away, and Eren grits his teeth.
---
"Ok. If you're going to date Armin, there have to be rules," he begins and Jean narrows his eyes.
"We've been dating for over a month."
"Details. First of all, you have to bring him home by 10 every night, no questions asked. I will not tolerate sleepovers unless there are other people present and you are in different rooms. No public indecency - in fact, no indecency at all. There will be no shirt lifting, booty calls, or wolf whistles."
"Ten? Armin doesn't even have a curfew!"
"He's allergic to peanuts, so make sure to check all the food labels first. If he has an asthma attack on your watch, I will personally castrate you and feed them to you. And last, but not least, don't you dare hurt him. If you ever make him uncomfortable, or god forbid, make him cry, I swear that I will make your every living moment hell."
Jean snorts, leaning back in his chair. "Of course not. You think I'd hurt him willingly? I'm crazy about Armin."
He doesn't miss the tender expression on Jean's face, the special smile he has reserved for the blond, and he sighs loudly. "Willingly or not, if you break his heart..."
"You'll burn me alive, yeah, I got it. Is that all you called me over for?" Jean grunts, getting up and making to leave. "Eren, I don't like you much, but I can promise you that I'm going to take good care of Armin, ok? I like him. I like him a lot."
Eren nods wordlessly as his teammate leaves and he falls onto the sofa. Armin and Jean are together, and apparently, they're happy. If they are, then he's in no position to stop them, right? He doesn't like Jean, and doesn't plan on ever liking him, but if Armin likes him that much, then maybe, maybe he can learn to get along.
It doesn't keep him from throwing a punch at the other's face when he sees Armin limping at school the next week, neck covered in barely-concealed bruises. He feels oddly satisfied as Jean walks away with a black eye. Yeah, that's right. If you hurt Armin, there's more where that came from.