Armin turned to lay on his left side, the soft moonlight shining through the window and lighting up his face. He watched the wispy clouds float by slowly for a few minutes before turning back to lay on his right side. He had been tossing and turning for about an hour trying to sleep, and getting no where.
Should I...?
He sat up and looked around, then crawled out from under his covers and made his way to the bed across the room. He hesitated, then lightly poked the occupant's shoulder. No response. He poked a tad bit harder, which elicited a sigh from the sleeper. He then poked him again and whispered "Eren... are you awake?"
Of course he's not awake, Armin thought. But it seemed like it was automatic, just the sort of thing everyone says without really knowing why.
Eren moaned softly and his shoulder twitched under Armin's finger.
"Eren, wake up." Armin whispered slightly louder, cautious not to wake the others. He placed his whole hand on Eren's shoulder and shook him gently, finally succeeding in waking his friend.
Eren's eyes slowly opened and he looked over his shoulder, blinking a few times in the darkness before recognizing Armin.
"Ar...min." he mumbled. "What... what are you doing?" his words were choppy and bordering yawning.
"I can't sleep."
"And?" Eren closed his eyes. "How does waking me up help?"
"Can I... " Armin hesitated. "Can I sleep with you?" he whispered quickly, his words too quiet and stumbling over each other. Eren was silent for a minute, trying to understand what Armin mumbled.
Eren let out a sigh and lifted his covers. Armin expression softened, showing how restless his night had been and that he was ready to sleep. He crawled under the blanket and scooted closer to Eren, snuggling into his chest. Eren snaked his arm around Armin, gripping his hair gently and letting his cheek rest on his head.
"Just like back then..." he whispered into his best friends soft hair before closing his eyes and drifting off to sleep.

A/N: By "Just like back then..." he means that when Armin would stay over with Eren or if he was taking a nap he would always sleep with Eren because he felt safer (just a little headcanon of mine- to clear any confusion on what Eren meant). I felt like writing a cute little Eren x Armin fic; you can take their relationship as romantic or just friendship, either is fine, neither is really specified anyways. I apologize for any misspellings or grammar issues, I didn't read through this (also for the sucky story I just wrote this in five minutes out of boredom) - Mako