In the academy, students spent a week focusing on olfactory memory. Certain odors can trigger different memories or emotional responses in a shinobi. This works even if the shinobi isn't all there mentally. It's good information for students interested in going into the Konoha Intelligence Division.
Sasuke had gotten perfect marks during that unit. And a year later, he looked at the streets of his neighborhood flooded with the blood of the Uchiha. The way his sandals squished in the soaked dirt, the deep confusion he felt as he saw lifeless forms in the receding light, or his heart pounding in his chest so hard that it was the only noise he could hear were all sensations he could make himself forget. When he walked on the edge of the pond near the Uchiha district in the preceding months, the sound of his steps against the mud did nothing to make him think of the slaughter. The scent that hung heavy and nauseating in the air, however, was another matter.
Years later, when tears of blood would run down his face and that coppery scent got to him, he'd still fight a grimace. The smell of blood and the concept of death were forever linked in his mind.
Naruto, on the other hand, bled like it was life-affirming. He would bleed to prove his heart was pumping. Sasuke never forgot the crazed look in his teammate's eyes when he stabbed his own hand when they were genin. Sasuke hadn't recoiled at the smell. It didn't even register. He'd been too focused on what he'd witnessed.
And when Sasuke had fought Naruto the following year, he watched their blood mix together and get thinned by the rain and felt like it was the most intimate he'd ever been with anyone. He hovered inches over Naruto's face, noticing the red pooling in the corner of the blond boy's mouth. It occurred to him to kiss it away, and he felt embarrassed for having such an impulse. As he fled, he imagined seeing Naruto again years in the future and exchanging blows. He wondered how many more times his chidori would hit Naruto's rasengan. How many more ounces of blood would be spilt. Who would kill the other first.
Every time they met again for years after that day, his eyes would linger on the corner of Naruto's mouth that he'd almost kissed. He'd never felt this way for anyone. His love wore a mask of violence. He had told himself that when he breathed into Naruto's ear that day in Orochimaru's lair, it was not out of tenderness. It was to taunt him.
They were children when they'd last bled because of each other. They had ripped one another apart and fell side by side, laughing and crying and he again ached to kiss the man next to him. No one could make him hurt like Naruto. No one could make him heal like Naruto.
Now that they were grown, there were dark circles under Naruto's eyes and crow's feet from years of smiling. Sasuke had wrinkles from furrowing his brow. He considered himself lucky to have lived long enough to see his companion aging. Somewhere in the back of his mind, though, he wondered how much longer they had. Which one would be the first to die. Shinobi like them did not get to greet old age.
Would he do things differently, if he could go again? Would he have kissed the corner of that blond boy's mouth all those years ago? He considered the weight of his sins, the map of mistakes that led him to where he needed to be. He imagines the reality where he had chosen to accept the love he didn't feel he'd earned. Where he'd remained in the village always, beside Naruto. He thinks they might not have gotten married to their wives, he might not clench his jaw and fist when he hears his name come out of Naruto's mouth. He might not spend so much time away from the village. He doesn't know if it was easier when he was younger and didn't know he was in love or if it's easier now that he has a word for his agony.