Orochimaru never felt things the same way other people did. Feelings for him are distant, like whispers through glass. Their purpose is practical - to aid in deciphering social cues and in manipulation - and that's it. He is a genius so naturally he became very good at deciphering and understanding the feelings of others, even if he doesn't care about them, even though he can't feel them himself. It makes him curious as to just how people worked and how they functioned efficiently with such obvious hinderances. He has come to the conclusion that they don't.
Orochimaru doesn't care about anything, especially things concerning the past. His whole being is focused on the future, his future specifically, and how to make it better and longer. The present only matters in the way it serves to enhance that future. The past doesn't matter at all.
But on slow days, when waiting for a test subject to transform or for harvested cells to multiply, if Sasuke is being particularly moody and Kabuto is away on a mission, if there are no screams coming from the lab, after a meal of three rice balls with a sticky spicy sauce, if it's particularly sunny and cloudless outside, and if he's craving his favorite tea, he just maybe allows himself to think on his old teammates. But only for the sake of research analysis on the complexities of the human condition. Yes, of course.
They are both such potent subjects for his analysis. All three of the Sannin had left Konoha for various reasons long ago. It made sense that they would all leave. The village could not contain such powerful, haunted people, nor could those people be suffocated for so long. But now he knows his old teammates have both found their way back to Konoha, and he vaguely wonders if it is a sign that he himself would one day return, if it is inevitable to go full circle. Orochimaru doesn't believe in inevitability or fate. He believes in plans and power...but he also believes in patterns. He is a scientist after all.
Orochimaru can picture them sitting in a bar, back in Konoha, after so many years, together. His smile is wide and her cheeks are red and they're laughing, because they've both always known how. He buys the drinks because he's a rich author and she has enough debt and he still pines for her. She accepts because he's an old friend and it's been a long day and hey it's free sake. She starts to forget why she rejected him for so long and he reminds her by signing a copy of his new book for a local fan. She's scowling now so he quickly pours her another couple of shots and tells a story about a monkey and a toad and they're laughing again.
Drifting back, Orochimaru remembers them in their youth. He sees a Jiraiya who has finally matured into the ninja he always swore he was. But he's still an idiot so he says something too loud and smiles and laughs with too much honesty for their world of shinobi. He sees a Tsunade still burning with an outward fire and confidence, but now using this to hide her missing pieces. She sends Jiraiya flying with a simple punch over his stray comment and bets a round of shots that he'll beg her to heal him within five minutes. He sees himself, wondering why she would break him only to heal him soon afterward. Wasn't it a waste of chakra? He accepts her bet because she always loses and it takes Jiraiya a whole fifteen minutes of obvious limping and stubborn curses to ask for help.
Further back still and there's a boy who can't throw a kunai straight and a girl learning to crush a pebble with one finger and a man who lectures with kind eyes and a boy who curiously watches it all. There is a strange warmth and the curious boy wonders where it's coming from and he never fully understands it and he hates this most of all. Orochimaru never fully understood them...but still, even after all these years, he knows them better than anyone else.
This is what he knows:
She gambles to prove she still has something left to lose. He writes to mourn for the happy endings he'll never have. Tsunade finds peace in the fact that she's only gambling with her own life. Jiraiya understands because he only gambles with lives of fiction. They both hate him for daring to gamble with the lives of others. They are both reaching for some large, unattainable dream because the small, reasonable ones have all shattered. They don't really believe they will succeed this time either, but it's something to do and there's an obnoxious boy who believes and reminds them both of loved ones long dead. They would both kill Orochimaru for what he did to their sensei, but not for the countless innocent lives he took. Tsunade hasn't quite managed to forget the quiet, pale boy who used to read old scrolls in the corner. Jiraiya won't let himself forget the black-haired prodigy whom he trusted completely. Orochimaru can't fully remember those past versions of himself but nonetheless imagines them to be rather lacking. He's never been very optimistic or much of a gambler, but he thinks maybe some whisper of a thought, a feeling that isn't his own, is telling him...
BEEEEP
The tests are done. It's time to wake the subject for another round of injections. The sun is setting and Kabuto is due to report soon. His tea has long since grown cold and it doesn't matters who those other people are or had been. A pale man with something to prove would claim that it never had.
But if Orochimaru compulsively organizes things in groups of three; if he color codes his notes in purple, red, and blue; if there's a dusty box somewhere containing a neon adult novel, an old medical tome, a scratched forehead protector, and three saké cups...no one in the compound is stupid enough to mention it.