Ever since they were young, for as long as he could remember, he always knew that Eren was a fighter. A strong willed, short tempered, confident boy, with the spirit of a raging fire locked in his small body.
Armin was something different altogether. He was passive, a quiet observer, hungry for knowledge, starving for the great unknowns beyond the walls.
How such a boy had been drawn to him, staying by his side all this time, Armin didn't know.
Was it because he was weak? To someone who took it upon himself to protect others, was he merely being pitied? He wondered sometimes; wondered even more when Mikasa showed up, becoming part of their newly formed trio.
The way he talked to him though, smiling excitedly as they looked through those forbidden books, asking him questions as if he knew all the answers, the way he'd come running and yelling at anyone who insulted him, it was almost as if they were equals.
But when the long-since-forgotten terrors of the titans returned, that petty illusion shattered.
Eren's fire had been smoked out, almost completely gone, before a new flame, dangerous and hateful, was lit. He was more fired up than ever, so much so it almost scary. He would kill them, he said, every last one of them.
Armin, on the other hand, was freezing over. He was scared, he was overwhelmed, and he was just waking up, realizing the awful truths of the world around him; he was weak.
But his mind, he slowly realized, was strong. Strong, but also very fragile.
The horrors all around him were almost enough to shut him down. And so he had to adapt; had to build up a stone cold wall of whatever apathy he could muster. It was all he could do to escape the guilt; because it should have been him. The weakest link; a useless soldier; a coward, clinging onto his own life; none of them should have died; it should have been him.
But Eren; Eren was always there, forever escaping that terrible fate. A candle burning brightly in the dark, just ahead of him. A constant reminder that hey, maybe he was good for something, that he had saved a life rather than watching it end.
If Eren was a fire, than Armin was, able to be soft or compacted, to freeze or to melt.
If Eren would go, Armin would follow.
If he fell behind, Eren would wait. He would help him up, pat him on the back, and flash that dazzlingly confident smile.
And the two would walk, side by side, until the day they made it out of that prison and finally saw the sea.