He really couldn't pinpoint when it happened exactly. They've been partners for 10 years at this point, and somehow it seems like it has always been this way.
Except in the beginning.
The beginning was all about evil glares and slamming doors. He swore that if looks could kill, he would have been dead a million times over in that first year alone. He was actually completely terrified in that first year or so of their partnership. Nobody would have known though, with that constant smirk and his cocky attitude.
The cocky attitude eventually brought out the famous raising of the eyebrow and continuous face-to-palm motions on her end. He somehow managed to make her giggle every now and then with his southern drawl and his impersonations of Nick Fury behind his back. It could have been the first time she giggled at his jokes…but he still wasn't 100% positive.
Sometime around the fourth year it all started to shift. It could have been here…but it could have been earlier? He wasn't confident on that. Not the point.
They got their first undercover assignment, and as always he was the rich businessman with his lovely wife on his arm. He didn't have to fake the fact that he couldn't keep his eyes off of her.
Now that Clint thought about it a little more it could have been then, but there was also many other times…
That year was all whispering intel disguised as sweet nothings in each other's ears and delicate smiles to play a part. Some soft kisses were exchanged, but not under their own pretenses.
It might have been in Budapest. That was the first time they managed to exchange a kiss on their own accord. Sure, she was quickly losing blood from the bullet wound in her lower torso and he was doing anything he could to keep her alive, but a kiss was a kiss…right?
He shed a few tears that day. He never left her side at the medical ward.
Even then it STILL didn't fully hit him.
She always said that he was pretty dense.
When she left for California and he traveled to New Mexico he got another wave of whatever the heck was going on in his chest. This was their first mission apart since they started working together. Nine whole years of being on the field with each other made Clint a little nervous. They were apart for a couple of months and he felt like he was having separation anxiety.
He called her so many times even though he wasn't allowed to.
But she called him just as often as he called her.
After the battle of New York it was a little bit more obvious to him. Even though they had their separate rooms, they gravitated towards each other. He would watch her do the most mundane things, like fold laundry or read a book in the sun, and that strange feeling in his chest would surface that he felt so many times before.
He admits it to her when she's braiding her hair one day randomly. He's sitting on his bed against the backboard just watching her when it spills out. She's fresh out of the shower, her hair slightly damp. She's wearing one of his old beat up flannels that has gone through hell and back and just seeing her in it is making his chest do that weird thing again.
"Hey, Tasha?" He says looking at her at the foot of his, no their, bed.
"Hm?" She asks, glancing over at him still braiding one of her pigtails. In that quick half a second of eye contact, everything made sense to Clint. The slamming doors, the quirk of a single eyebrow, a small giggle, a whisper in his ear, a desperate kiss, a midnight phone call, it all finally came together in that one flash of her bright green eyes.
"I think I love you."