The thing about Tony, well, one of the things about Tony, was that he had very little shame when it came to what he did alone in his bedroom (or with a partner in his bedroom, or with several partners, or not even in his bedroom maybe somewhere more interesting like one of his lounges, or one of his cars, or in a broom closet, or in the Spinning Teacups ride at Disneyland); suffice to say that Tony just generally has very little shame when it comes to anything sex-related. Because of this, and because he’s still not used to living with people, he never locks his bedroom door. Sometimes he doesn’t even shut it properly, leaving it slightly ajar while he does whatever it is he does alone in his bedroom.
Pepper, as part of her job being to occasionally make Tony get out of bed and go to work, has walked in on Tony in compromising positions so often that it barely phases her anymore; Rhodey has been Tony’s best friend for so long that apart from a few token protestations he basically can take anything in stride (although he refuses to ever talk about that time they got so completely drunk in New York that they woke up with no memories of the day before in a random hotel, in the same bed, naked and spooning, with four chickens in cages in the corner of the room).
When it came to the other Avengers though (Tony was a superhero, on a superhero team, lead by Captain America, and they all lived together in his place – Tony’s life was awesome), their reactions were a little more varied.
When Clint walked in on Tony masturbating, he shrieked and threw his malfunctioning mobile phone at Tony, and because Clint has great aim and is a massive asshole the phone shot through the air at great velocity and hit Tony square on his balls.
Basically, Clint is a bastard and Tony is not fixing that phone.
When Thor walked in on Tony masturbating, he complimented Tony on having a great looking dick and after Tony came with Thor’s hand around him he returned the favour with a blowjob making the appropriate and completely necessary joke about this being the only time he’d consider getting on his knees and worshipping a God. Thor laughed, and his semen tasted like apples – which was actually pretty freaky. Thor said something about special apples keeping the Aesir young and that must be why, but to be honest Tony wasn’t listening because he was trying to rub feeling back into his jaw. Tony had expected a god-sized dick, but holy crap.
Basically, Thor is apparently also a fertility god and Tony shouldn’t have been surprised.
When Bruce walked in on Tony masturbating, he blushed and stuttered before taking a breath and telling him that Clint was making pasta tonight, if he wanted any. Also, he’s free tomorrow night if Tony feels up to doing anything – if you know what he means – and no really, anything.
Basically, Bruce is making up for lost time after not being able to have sex for the past few years and Tony has made it his duty to have sex with all the attractive science nerds he meets.
When Natasha walked in on Tony masturbating, she didn’t even blink as she told him that she couldn’t make their sparring session tonight because SHIELD wanted her in for some classified stuff. Then she dropped her eyes to the vibrator he had been about five seconds away from shoving into himself and said that she had the same one, but she’d found that the highest setting wasn’t actually very high and Tony agreed but he adapted it to make it better and he can do the same to hers if she wants?
Basically, Natasha is completely unconcerned with Tony’s sex life and Tony feels like it should be weird that he bonded with Nat over similar tastes in vibrators.
When Steve walked in on Tony masturbating, he paused for a split second before going, “Oh, sorry” and calmly walking away, making sure to shut Tony’s door after him.
Basically, Steve was in the army in the forties so he probably got inured to seeing his teammates wanking about seventy years ago, and Tony comes ridiculously hard with Steve’s face in his mind.
That last bit might be an issue.
As it is, the facts are these: Tony has no shame when it comes to sex; Tony doesn’t believe in shutting or locking bedroom doors; the other Avengers don’t believe in knocking on bedroom doors; and Tony’s new favourite wanking material has been featuring Steve an awful lot lately.
All of this might never have come to anything, except it does. And it is only, like, 35% Tony’s fault (50% Steve’s fault for being so fucking hot (which in itself is probably 50% Howard’s fault which Tony will not be thinking about, thankyou), 5% Mom and Dad’s fault for not giving him siblings so that he’d have the meaning of a closed door put into his head at a young age, and 10% the other Avengers’ fault for not establishing early on in their living with him that one is expected to knock before entering someone’s bedroom).
So Tony casually walks into Steve’s room one night. Not for any particular reason, thought maybe Steve’d be interested in a late night movie, whatever. Except that when Tony opens his door Steve is in no condition for watching a movie. He is, in fact lying with his legs spread wide open, giant throbbing erection, and a blush that goes all the way down.
But there’s more to the story than that, to get a full appreciation of the sheer wonderment and arousal that Tony is feeling at seeing Steve feeling (himself) the narrative must pause for something that Tony likes to think of as the “Greatest Hits of the Most Frustrating Unresolved Sexual Tensions (That Are Eventually Resolved) of the Twenty-First Century: Steve and Tony Edition”.