It seems like like such a silly observation to make, and she's sure that if she ever were to say it out loud, he'd never let her hear the end of it – But he can hardly expect her not to spend any time looking at his face, or thinking about it, after went and changed it.
He has, as far as she can tell, roughly four distinct types of smile, that he employs depending on the context and the situation, as vague at his grasp on both these concepts can be at times.
The most frequent is, of course, the cheeky, cocky one he wears whenever he's in the process of showing off, or about to about to outwit someone, which essentially amounts to the same thing. He thinks he's so incredibly smart sometimes, and the worst is, he usually is, which makes the few times he isn't all the more elusive to him.
She may not be completely innocent in that department either, she absolutely got the feeling behind it, but in the end, it was always her who ended up having to convince the locals to put up with him long enough for him to get them out of whatever mess they had gotten themselves into this time – but at the end of the day, when the problem was solved and he paused to do one of his little victory dances, the corners of that small, pleased smirk refusing to be suppressed, his attempt as a dark, imposing-looking costume subverted by these ridiculous white dots on his dress shirt, she wonders how it's possible that she ever failed to see him.
Then, there's that one grin that she would, and probably had recognized in a thousand different times and places, the one that looked so utterly the same no matter what face he wore, so very contagious, wide, plastered everywhere, taking over the eyes, brimming with excitement, unfailing in the face of danger, when he was running towards the nearest explosion.
It was usually a sudden, momentary thing, but liable to stay for a while if he found something to gush about.
There was just some very particular, characteristic feature about the way it spread out from within, the wild, manic sparkle undimmed by the years, and it assured her that, no matter how much suffering he might have to face, his passion for this world was something he would never give up.
She had seen the bittersweet one quite often on their many adventures, a sight that was unexpectedly frequent on his last face when she stopped to think and consider it, which was probably why he'd done his best to avoid considerations like the plague; He'd try his hardest to conceal it all, to hold on to his ideas of wisdom and the resolve that such important moments deserved better than just sadness, but insidious as it was, the combined weight of lifetimes of loss, tragedy and regret would always seep through, hinting at a wealth of realized implications and similar stories he was only just holding back, connections and images that might occur to someone who knew his whole story, words he wished to say but decided to keep to himself, because it wouldn't be fair, because it wouldn't help, because he had much to atone for and aware that he should be starting right here, by putting someone else first, and it was moments like these that had her thoroughly convinced that, for all his flaws, imperfections and ambiguities and all the times she's wanted to smack him in the face and never see it again, she could never fully hate him with all of her heart, this man who'd readily give up all of himself to protect the ones he loved.
And she'd thought that was all of it, once upon a time, she though she had it all ordered and categorized, at least as far as the rough outline went, but it was then, after their venture on the Orient Express, when she though she had just gained another chuck of understanding, when the uneasy progression of her still uncertain feelings led her to a point where she decided that she would be staying with him after all, he went and surprised her all over again with the way his features just melted into pure bliss, every bit as unfiltered as his harsh comments or darker musings could be, restrained only perhaps by a tinge of absolutely hopeless, school-boyish awkwardness around the corners.
It's not warm, exactly, but she can't come up with a good word to describe it without squeezing it too much into one particular interpretation and leaving out some of the many things it seems to express; The best she can manage is to call it "pretty", in the way a little girl might describe anything that makes her happy.
And she's also positive that she's seen this somewhere before in all the time she's known him, but she can't say when, perhaps it was always mixed up with something else, or maybe she hadn't learned to notice, maybe she hadn't payed attention to the right things;
When she thinks back to their earlier travels, there are obviously memories of moments that were difficult, but the default images that come up within her mind are of them always smiling, always happy together. Right after he changed, there were times when she wondered how long it had been since she'd last seen anything beyond cold harshness, anything positive at all come from his direction, but as he stands before her now, she is suddenly fiercely glad to know that he wouldn't bother with the pleasantries, because it wouldn't actually make the difficult situations any better, and she's seen that he'd rather face her disappointment than give her false hopes that will do her no good;
And because it allows her to know that, when he smiles at her like that, beaming like a newborn star, like the whole of his world raises or falls with her answer, it is as genuine as anything in this world can be.