disclaimer.../\ Naruto belongs to Kishimoto Masashi. Writing belongs to me./\ I have a habit of making characters whose scariness is debatable grow up into at least somewhat intimidating individuals. In each and every one of my fandoms, I do this to at least one character. Naruto-kun is my victim, here.
When he's twelve, the deadlast's stupid grin is wide and blinding and has gotten very old very quickly, yet, Sasuke fully expects to see it.
When he's sixteen, he hasn't seen it for years, and has forgotten why it seemed like such a normal part of his day. Rusty feelings rise up and fetter for a few hours afterward, because Naruto smiled at him with some sort of knowing approval, which by all means he shouldn't have, not when...
"I will definitely bring you back to Konoha, Sasuke."
If he'd ignored the threat and stayed, would the Rasengan have hit?
He's twenty. Uzumaki's grin is less of a smile and more of a bearing of teeth, broad and vicious—cerulean eyes sharper and more unsettling than a dumbass' ever should be—and he is a ninja, a demon nin, as fang-toothed as jinchuuriki ought to be when in control of their power, but the loyalty and senseless love and overall emotion remains, matured and just as unwavering as the first time Team Nine nearly died for each other; traits a monstrous bijuu would never possess.
The surprisingly deep tones and words that tumble off the blonde man's tongue are more effectual than Sasuke thought he'd ever hear from someone who still wears spots of orange here and there, but, as he continues to listen, there is unmistakably a certain air of casualness in the small nuances of body language, intensified by distinctive inflections and bursts of vocabulary (bastard, precious, can we finish this quick, I have a date with ramen later) that slap him in the face with the fact that yes, this is the annoying kid you called brother and left behind. He's all grown up now, did you hear?
The familiarity is not gone, it lives in the creases and small twinges in the fox container's face, and the literal last Uchiha wonders what he would do if he decided to act on them.
