unbeta'd
"After his death, Armin mentions that they usually performed equipment maintenance together." - From the SNK Wiki Entry for Marco Bodt
Equipment Maintenance is always done in pairs, and the pairs are always chosen alphabetically. This is to ensure that everyone takes their turn, but with the 104th Trainee Squad it often leads to problems; alphabetically speaking, K followed J, meaning that Eren Jaeger and Jean Kirschstein would have to work together after training,usually when they were both irritable and tired. Whenever it was their week, the instructors would look to the trainees, almost as though they were desperate for one of them to volunteer. And Marco would volunteer, honestly. He'd willing take Eren's place if it meant the instructors didn't have to go back later to check the two had actually performed any form of equipment maintenance. But he never did.
The way Marco sees it, volunteering to take Eren's place might trigger something in the instructors minds that could result in them swapping partners. Everyone else probably views this as the ideal outcome, considering Marco's partner for maintenance is Armin Arlert, Eren's best friend. Eren probably hopes that Marco will ask to switch partners; the boy would probably ask himself, but asking would mean showing spending time with Jean had gotten to him, which would mean Jean had won.
Marco doesn't know if he'd be able to switch partners. He doesn't want to lose that carefree conversation, those nights of pleasant babbling as they polish 3DMG and stack gear and take inventory. Because that conversation has come to mean a lot to Marco, even if it mostly consists of idle chatter. There's something wonderful about listening to Armin talk about his dreams, his passions, his goals. Maybe it's the way his voice picks up, or the way the corners of his mouth twitch into a relaxed smile. It could be the little hitches in his breath when he huffs cheerfully, almost as though he's laughing at a joke he hasn't told. Then again, it could be the way his eyes light up and gleam when he looks up, a bashful blush playing across his face as he mutters an apology for getting too carried away with what he has to say.
He listens to Marco's dreams too. He listens and he doesn't judge. He doesn't scowl like Jean does, he doesn't tell Marco to stop lying, he doesn't accuse him of wanting anything other than to protect the King, and that's something that Marco really appreciates. It's nice to be believed. It's nice to talk to someone who doesn't think he has ulterior motives for wanting to join the Military Police. It's nice just to feel... almost accepted, he supposes.
Being around Armin is comforting. The conversation comes naturally, the pauses never feeling awkward. It's one thing, Marco thinks, to be able to have a comfortable conversation with someone, but to let that conversation fall into a comfortable silence is something else. Just being with Armin and knowing that he doesn't need to say anything, but could if he wanted something makes him feel so free.
He doesn't know if Armin feels as comfortable around him as he does with Armin. He hopes he does, but he doesn't know for sure. He certainly doesn't think that this shared chore means anything to the blond, but boy, does it mean something to Marco. He wishes sometimes that he could just sit with Armin at dinner, or start a conversation with him in the barracks, or just say anything to him outside of Equipment Maintenance, really. Because his heart speeds up when he sees that passionate gleam in Armin's eyes, his pulse races when he flashes him that timid smile, his breathing slows when he notices the boy tuck a strand of that golden hair behind his ear because it was getting in the way or annoying him or whatever long hair does.
Falling for Armin Arlert was certainly not something he intended to do, and yet he knows he's done it. Furthermore, he knows that whether or not Armin considers him a friend, these feelings Marco's developed are one-sided, and he'll never doubt it.
Maintenance is a pain, a literal pain, because it is so hard to see that smile once every few months, so hard to hear that voice, to talk about trivial things in such a relaxed way, the whole time knowing that it'll all end as soon as the chore does. That Armin will just go back to Eren and tell him how boring Maintenance was and how tired he is. Because it's Eren, and it always will be. It's Eren that Armin grew up with, Eren who was there with him on that day, the day Wall Maria fell. It's Eren who Armin will go to see the ocean with one day, along with Mikasa. It's not him, it's not Marco.
It's not Marco and it never will be.