Sirius had always been the adventurous one, the one with a plan, the natural-born leader. Remus, quiet and affected, felt like a whole different person when he was with Sirius, a person who was brave and strong and just a little bit wild. Sirius brought out a part of Remus that Remus hadn't known existed.
They'd met when they were eleven, young and shiny-faced, thrilled to pieces about their new school, far away from their parents for the first time in their lives. They were all in a dormitory together: brave, reckless Sirius, handsome, intelligent James (he'd always been handsome, right from the start, and so suave), seedy-but-loyal Peter (who could be trusted for his stash of sugar quills and Firewhisky, if nothing else), and Remus. Plain, quiet Remus, cripplingly shy from years of being isolated from other children and the prying eyes and hushed whispers of strangers.
On that first night, Remus still floating from the wonder of his bright glorious future in a place where nobody knew about his secret, sat on his four-poster bed and watched, aloof, as the other three boys goofed off, tossing about a Snitch-shaped pillow procured from James' trunk.
"Eyyyy!" Sirius climbed up onto the bed, flinging an amicable arm around Remus' shoulder. "Come play, yeah?"
Remus blinked and declined politely. "No, thank you. Didn't the head boy say it was time for lights-out?"
Sirius laughed, loud and long, as if Remus had just told him a particularly funny joke. "My dear boy," he said, eyes twinkling with something Remus would come to think of as Siriusness, "Didn't they ever tell you that the rules were meant to be broken?"
With that, Remus became part of Sirius' group, and spent every waking moment with them, talking and joking and skiving off Charms. They called themselves The Marauders, on Remus' suggestion: marauders were rogues, and rogues they were, somehow managing to get the most detentions in Hogwarts history in their first two years. But it was Sirius to whom Remus connected most genuinely, Sirius to whom Remus told his deepest secrets, Sirius whom Remus loved. He realised it in third year—while the other boys (Sirius included) had begun to notice the girls, even begun to date them, holding hands on the way to potions and chastely sharing Butterbeers on Hogsmeade visits, Remus found himself unable to stop thinking of Sirius, of the way he walked and talked and laughed and smelled, the way he wrapped an arm around Remus' shoulders and sang ridiculous Muggle songs from some war that they'd learned about in Muggle Studies, the way he walked about without a shirt after Quidditch practise.
"Could I talk to you?" Remus asked nervously, one day three weeks before the end of third year. They were alone in the dorm, Peter and James having gone 'out for some air' (in other words, sneaking off to Hogsmeade in the Invisibility Cloak), sucking on sugar quills and pretending to do transfiguration revision. He'd been planning this speech for over a month, and had spent the morning in the toilets, practising an air of nonchalance when Sirius, horrified, retreated from the dormitory and never spoke to him again.
"Yeah, go 'head," Sirius mumbled around a mouthful of quill.
"Sirius," Remus whinged, "this is serious."
They shared a nervous giggle at that, and then Sirius set his quill and parchment on his own bed and climbed onto Remus'. "What's going on?" he asked, wrapping his arm around Remus' shoulder. Remus shuffled away, folding his hands in his lap. Sirius looked expectantly at him. "Yeah?" he encouraged.
Remus took a deep breath. "I have a friend…he's sort of going through something. He's started having certain feelings…for, for his best friend. Certain, er, sexual feelings. And even though he knows that his friend doesn't share these feelings, he feels as though it's unfair to his friend to withhold them any longer." Remus had closed his eyes at the beginning of his speech, but Sirius' breath near his shoulder made them snap open. "What makes this friend so sure that his friend doesn't share his feelings?" Sirius whispered, warm and ticklish against Remus' ear.
"Well…" trying to keep his breathing even, "I reckon he likes girls."
"You reckon wrong," Sirius mumbled, turning Remus' face to his own and gently, awkwardly kissing Remus' mouth. When he pulled back, he took Remus' hand in his own. "I have those feelings for you, too."
And then, as if nothing had happened, he climbed off of the bed and went back to his revision.
They didn't speak of the kiss again, but after that, their relationship deepened in some subtle way. Their hands brushed sometimes as they walked to class, or Sirius would turn around and give Remus a look, one that was translated by the outside world as "this class is boring", one that really meant "I love you. Meet me in the toilets after class." They never spoke of it to anyone. It never occurred to them that they should. This way, Sirius could go on being one of the most popular boys in their year and Remus could go on being the pale, sickly boy who hung around him without complicating anything.
And now he was gone, and Remus couldn't help but wondering. If they hadn't hid it, maybe their love would've been enough to save him. But Sirius had always been the adventurous one, the one with a plan, the natural-born leader. They'd been playing those roles for so long that it had never occurred to Remus, in all the time they'd been together, that someday they'd need to reverse, that someday it would be time for Remus to be the leader and for Sirius to stand back, to let someone else be in charge for a moment.
"But what's life without a little adventure?" Sirius had asked him, just before he died. "What's life without the thrill of not knowing what's to come?"
"A life without you," Remus said now, running an affectionate finger across the surface of the photo he held in his hand. "A life without adventure is a life without you." Then he set the picture down in its hiding spot under the rock and walked slowly back to the house, back to his life without Sirius, his life without adventure.