Title: Subjective Permanence

Author: ELLE

Pairings/Warnings: Tony/Pepper/Bruce, explicit language, explicit sexual content, exhibitionism, voyeurism, fingering, masturbation

Notes: I may or may not have gotten this idea from a gif I stumbled across so yeah it's pretty much just straight up porn. Also a special thank you to tonysbruce for her encouragement because without her this would definitely never have seen the light of day haha.

At this point in his life, there were very few things Bruce Banner was scared of. General Ross? Sure. Losing control of the Hulk and flattening a city? Obviously. But he'd been living in Avengers tower for a little over six months now and it wasn't until he walked into his and Tony's penthouse room and saw Pepper standing there that he realized he was scared shitless of her.

They had been living with a tenuous understanding of how their mutual relationship with Tony worked for the past few months and it generally entailed a lot of avoidance. Tony split his time pretty effectively between Malibu and New York and since Bruce couldn't really leave the tower, Pepper stayed in California.

Still – Bruce was acutely aware that she owned everything that he considered his and he was just a visitor she benevolently let overstay his welcome. He didn't think about it often, honestly, Tony never gave him much of a reason to – but to see her standing there, poring over the little collection of books he had started building, made panic grip his chest in a way he hadn't felt in months.

"Oh," Pepper said, straightening up and setting the book she had been perusing back on the shelf along the wall. "Hi Bruce."

He tried to swallow and still the rolling in his gut. She was smiling, trying to be non-threatening, but all he could imagine was that his time here was over and this was the beginning of the end. How stupid he was to think he could stay. This room was Pepper's, this tower was Pepper's, and Tony was Pepper's. She wasn't wrong to come claim what was her's. He wasn't mad, just... disappointed. In himself. For believing Tony every time he said it was okay, that he was home here.

"Pepper," he acknowledged, hating the tremor in his voice but he couldn't stop it.

Of course she noticed it and her smile tightened a little. She stepped across the room – so naturally, like she belonged there, which she did because it was her's – to the bed he slept in every night and made every morning, running her fingers across the duvet before sitting down on it. Then she looked back over at him and smiled, patting the space next to her.

"I had a meeting I couldn't avoid in the city this morning and thought, as long as I was here, maybe we could talk?"

She had that open, optimistic look that women had when they were trying to be comforting and, seeing no way out of it, Bruce consented with a hesitant little nod of his head, keeping it down as he approached with caution.

He sat down next to her on the bed, trying not to twist his hands. It occurred to him in that moment that he had never been alone with her before. The few times she'd been here since he came to live here he'd either disappeared to the lab or faded into the background as much as possible. Which, when Tony was around, was easy. It was something he greatly appreciated about the other man.

But now he found himself cursing Tony over the fact that he wasn't home yet.

"Bruce," Pepper started with a bit of a sigh, smoothing her hands over her expensive white skirt. "You know, I'm not here to change anything."

She gave him a moment to process that. And it did take a moment. But though she'd said it plain enough Bruce found couldn't completely trust that, not really, because... why else would she be there?

"Although I sometimes hate to admit it, this has been good for Tony," she continued, folding her hands together. "And... for me."

Bruce had been very careful to keep his eyes on his knees up until that point. But it was so the opposite of what he'd been expecting to hear that he found himself turning his eyes upward to look at her and gauge her sincerity.

"I was skeptical at first but – we are both happier," she continued, offering him a tight but honest smile. "Tony can be a little..."

"Overwhelming?" Bruce offered and Pepper snorted a little laugh that seemed so, just, real that Bruce found himself easing up.

"Well, you know how he is," she said with a smile, looking over at him for a moment too. "He's just so – there's so much going on and I... I can't really keep up. He's all possibilities and I live by absolutes and I don't want to get frustrated by him because I love him but... I do."

Bruce shrugged in solidarity. "He's frustrating. Brilliant, but... frustrating."

For a moment they were quiet but it was... okay. Bruce still didn't know why she was there but he didn't feel like it was malicious, more like she wanted to commiserate with him. Which he understood because as much as he loved Tony too, he was sometimes grateful when he left for a conference or California and Bruce got some time to himself to decompress. It was just who he was. He needed time to be alone.

"The thing is," she started after a minute, tentative, raising Bruce's hackles and he eyed her warily, "it would be easier for me if I could come here sometimes."

Bruce felt a little taken aback to hear her say that after all the time he spent reminding himself that his existence here was due wholly to her kindness.

"This whole tower is yours. I know that."

"No!" Pepper corrected quickly, her mouth dropping into a frown. "You live here and I don't want you to feel threatened by me. What I want..." She paused and looked back at her hands a moment. "What I want is for us to be friends."

Bruce blinked. Friends? He had to admit – the idea caught him off guard. Very few people had ever wanted to be his friend and he had no idea what he could possibly offer Pepper.

"Okay," he agreed carefully.

She tilted her head, red hair falling over her shoulder in a cascade as she held out her hand for him. He was still a little unsure, but Bruce placed his within it and she squeezed.

"I've – I'm embarrassed to admit this," she said, eyes falling to their hands. "But I've read about this – what we –"

Pepper stopped abruptly, sighed out a laugh and Bruce put his other hand over hers, holding it. She looked back up at him with a small, grateful smile.

"I know what Tony sees in you," she said. "I think, in some ways, you're a lot like me."

Bruce wasn't too sure about that, but given that he didn't really know her, he chose not to say anything.

"I don't want to invade your space or your privacy but maybe – one day – it would be nice if I could sleep here sometimes – with you."

Although it wasn't the first time he'd thought it in the last five minutes, nothing could've been further from what Bruce expected. He stopped and stared, expecting her face to change or for her to say "gotcha!" or... something. He was reduced to monosyllabic questions.

"What?" he asked. "Me?"

She withdrew her hand in a defensive gesture but still looked at him, still smiled.

"Of course I understand if you don't –"

"No," he corrected, feeling like – this was good, this was good for them, for Tony, and he didn't want her to misunderstand. "I'm just... I wasn't expecting that."

Pepper's smile was a little easier now and she reached back for his hand, placing hers over where it sat on his knee, rubbing her thumb across the top of it.

"I thought –" he laughed, suddenly, shaking his head as the last bit of tension he felt at her presence here disappeared. "I thought you were going to ask me to leave. Which – would've been okay, I would've –"

"Oh, no," she assured him, her shoulders relaxing too. "I've never had a problem with you – I want you to know that." Then she dipped her head, almost shrinking and looking very girlish for a moment. "I hope you see me as more than just a benefactor."

"I... sure," Bruce offered, a little more confidently than he felt. "I think I... can. But." He stopped, looked at her a little more closely. "You... read? About... threesomes?"

Pepper's face blushed bright red before she had a chance to hide it and she smoothed out her skirt again and tried to regain composure.

"I did," she stated as if it was no big deal, as if she wasn't embarrassed about it.

"And?" he asked, a mischievous little grin threatening to overtake his face. Maybe he was starting to understand what Tony saw in Pepper.

"And apparently it's not all that uncommon for all three people to sleep together." As if realizing the implication of what she said, she quickly added – "In the same bed. Just sleep, you know. Not. Whatever. Though obviously that too. But not for us!"

Bruce was flat out laughing now and despite her clear humiliation, she was smiling too.

"Not for us?" Bruce teased, finally truly relaxed, leaning back on his arm as he smirked. "Even this big bed is going to get a little crowded."

"Obviously Tony would sleep in the middle," she stated so matter-of-factly Bruce couldn't help but laugh once more.

"You've really thought this out, huh?"

"No, I just –" she started, then stopped, her smile betraying her. "...maybe a little."

"Then surely you've realized exactly how that would go," he prompted but Pepper just blinked rather naively. Bruce raised his eyebrows and when it finally hit her, she just covered her face with her hand, shaking her head.

It didn't really bother Bruce. He wasn't particularly used to being the object of anyone's affection – in fact he still found it puzzling that Tony found him genuinely sexually attractive. So he wasn't offended by Pepper's obvious rejection – it was exactly what he'd expected.

"You're right," she agreed, face pink. "I thought, maybe, one day, but that was just – I'm sure you have no interest in that."

Bruce just nodded for a minute until his brain had time to process what she'd said.

"Wait," he mouthed, stunned. "You would... With me?"

Now Pepper's face was beneath both of her hands but the blush on her ears gave her away.

"I'm only human!" she said to her hands. "Of course that is something I would be interested in!" Bruce started laughing and she moved her fingers enough to shoot him an irritated look from the corner of her eye. "For some people that's the entire point of letting their boyfriend have a boyfriend. And it's not like Tony doesn't have... experience with... that."

Bruce laughed and it encouraged her to put her hands down and meet his eyes again.

"I'm making this into a me thing, Tony must be rubbing off on me," she sighed, fingers grasping each other, a nervous little gesture that was very endearing. "If you never feel interested in that, I completely underst –"

"Hey," he said, reaching out and touching her knee carefully, not wanting to invade her space but wanting to make it clear he was okay. "It's okay. I think – I would like that too."

Pepper smiled then, that beautiful smile that Tony had as his phone background, the very expression Bruce conjured up for her when he heard her name.

"We can't let Tony have all the fun, right?" he joked and for a moment there was a certain levity between them that Bruce had never dared to hope for.

For a moment they simply sat there, Bruce moving his hand off her knee and onto his own, unsure exactly where they were supposed to go now, until Pepper tilted into his space a little, bumping his shoulder with her own.

"Do you want to... try it?" she asked cautiously and Bruce stared blankly, trying to ascribe an act to 'it' without doing her the disservice of presuming.

"Kissing?" she filled in when it was clear Bruce wasn't going to reply and he was grateful for how forward she was.

"I –"

But instead of letting him answer Pepper leaned in further, lips just barely touching his. And Bruce leaned in a little bit too, pressing a little, uncertain because she was Tony's, she had always been Tony's, and he knew how much Tony cared for her and he was so clumsy and she was so gentle and he didn't want to hurt her, to break her, the way he broke everything.

Pepper reached out for him though, slipping their fingers together, drawing him in as her lips closed around his, nipping at the bottom one slightly, teasingly. Bruce grinned just a little and as Pepper pulled away he initiated the next kiss, darting his tongue out to meet hers tentatively. And she indulged him, kissing him back more thoroughly, more confidently, and Bruce felt like this was okay, in fact this was good, this was even... fun?

It made sense. Tony was a very eager and inventive partner and he liked to have a good time. Bruce knew beyond a shadow of a doubt that he was head over heels in love with Pepper, in a way that wouldn't be possible if she didn't at least try to match his passion and vivacity. He sure as hell knew Tony wasn't sleeping with him because of a lack of anything in Pepper – they just had a very different relationship Tony appreciated in a very different way.

"Not so bad, huh?" Pepper asked as she broke the kiss, brushing at her bangs, clearly a little self-conscious.

"You tell me," he replied with a smile, trying to put her at ease. "I have no complaints."

Instead of replying with words, Pepper simply leaned forward again and with more confidence Bruce moved his hand to the back of her neck, stroking his thumb across her cheek – a little more intimate, a little more him – and she hummed this slight hum of approval that, much to his surprise, sent a spark shivering down his spine.

Encouraged by her body language Bruce moved his other hand to her back, running his hand down it, and Pepper sighed against his lips, moving her fingers through his curls, down his neck, her touch comforting and welcome. It seemed strange he had been so terrified of her when she was this gentle and kind.

Then she laughed, soft and genuinely amused and for a moment Bruce was thrown off, unsure as to why when he realized his hand was on her ribcage, his thumb tucked up beneath her breast. Quickly he dropped both of his hands, embarrassed. It had been a long time since he'd kissed a woman and he guessed he got carried away in the moment, muscle memory from Betty, latent desire...

But Pepper didn't seem to mind as much as he did and she grinned, reaching for his hand again.

"It's okay," she assured him, putting his hand back on her body. "I like it."

Bruce was heartened by that confession and leaned back in to kiss her again, running his thumb over her breast, feeling her nipple hard beneath her thin cotton shirt and the little gasp she made amplified the spark from earlier and sent electricity jolting through him. Pepper arced towards him, clearly wanting more and his other hand moved to her waist, supporting her as he brushed his thumb by again.

And then, quite suddenly, they were moving towards the headboard, he was laying her down against it and she was drawing him in close with her arms, hands on his face, lips desperate to meet his again.

It was as strange as it was wonderful. With Betty – it was raw, unadulterated. He wanted her in ways that weren't right. Betty saw him and she wasn't scared and he wanted her – her acceptance, her compassion, her love. He wanted her to be everything and... it wasn't fair. She couldn't be.

With Tony – it was easy and effortless. Tony saw him too but it was less personal, less needy. Tony had his own goals and interests and needs and Bruce knew that he could never be Tony's everything – and that was okay. That was good.

Now, with Pepper, it was just... well, it just was. Impersonal lust. Mutual interest. There was nothing there and yet there was. It was a beginning. It felt good. He tried not to question it.

Instead he found himself slipping the top button in Pepper's shirt, then the next, exposing a sheer mesh bra that he could see her perfect blush nipple through. They kissed again as Bruce slid his hand into her shirt, cupping her breast, feeling her hard nipple on the palm of his hand. His pants felt entirely too tight. He fought to get his heart rate under control before this became an entirely regrettable situation.

Pepper shifted, giving him a very welcome moment to breath, pulling up that pencil skirt a bit to give her legs a little more freedom and then she moved her hands to his belt. It hadn't really occurred to Bruce until that moment that he was actually going to do it, he was really going to have sex with her. Of course he could turn her down but... he didn't really want to. So at this point the best he could do was hope that he could hold a candle to Tony, which... he knew he couldn't.

She unbuckled his belt but in a moment of anxiety Bruce shifted up next to her, his hand on her thigh as he met her lips again. Kissing was easier, it was easier to be in control, but Pepper moved so that his hand slid further up her thigh. He doubted he had very much control at all.

It was hard for Bruce to give up control, but Pepper made this delicious sound as he slipped his hand up under her skirt and he finally relinquished all thought. Tony and what he would think when he found out, Betty and how she would no longer be the last woman he had been with, Pepper and what this meant for the future of their relationship – all of it faded into the background as his hand reached her panties.

Pepper hummed a sigh of consent as he moved them to the side, running his fingers along her, feeling how wet she was. Bruce couldn't contain the moan that fell from his lips as he moved them trembling to her neck. His abs clenched with the strength of how badly he wanted her then, pressing his palm against her clit and feeling her shift her hips against it as he slid two fingers in her.

"Fuck," she almost growled, surprising Bruce, but also making him pause to catch his breath.

Every sound she made was driving him mad and it was so much like Tony it sent him straight back to the first time Bruce had fingered him, cursing and needy, driving his hips down on his hand. But Pepper was different, less anxious, and she rotated her hips slowly, relishing it as he slid his fingers in and out, adding another, slicking her wetness against her clit with every push.

His face was on her chest now, kissing down that wide expanse of skin to her breasts, wanting to taste her. It had been so long. Bruce ached for it and Pepper spread her legs wider, pushing her skirt up further, knowing where he wanted to go, encouraging it, wanting it too.

It was then he noticed the stifled groan that wasn't his own, glancing over Pepper's leg to see Tony leaning heavily on the bureau pressed up against the opposite wall, pants undone and hanging off his hips, hard dick out in his hand and Bruce was torn between being ridiculously turned on and fucking pissed. He sure as hell didn't agree to be watched like that, and Pepper didn't either – although, maybe she did? Because she nudged him with her knee, egging him on, spreading herself out more provocatively and she had to have seen him.

For a moment longer, Bruce hesitated, vacillating between wanting to chew Tony out and wanting him to watch but in the end wanting him to watch won out. Bruce didn't have a particularly voyeuristic nature – he got enough of that being spread across TV screens as a monster. But... he liked the way Tony looked at him, with heavy lidded big brown eyes, full of desire and passion and as close to whatever kind of love they could have. And Tony was certainly looking at him now.

So Bruce lowered his head between her legs, feeling her fingers on the back of his neck, running up through his hair, fingernails tracing along his scalp in a way that felt remarkably good as he went down on her.

Bruce could never be accused of not being thorough and with each experimental touch he studied Pepper's reaction until he nailed a combination which had her thighs tense around his head and her fingers twisted in his hair. He slicked his tongue over her as he worked his fingers inside of her, feeling her body start to trembled and her breath catch in her chest as she rode the line. Tony cursed, clearly trying to muffle it, but it was enough that Pepper couldn't hold it back any more and she gasped as she came, her body clenching up and she pulled his head up onto her stomach as she relished in her high.

He glanced at Tony, eyes closed as he sighed, tugging half-heartedly at his dick, prolonging the pleasure of his own orgasm a moment and for a minute, no one moved. Tony leaned against the dresser with a grin on his face and Pepper ran her fingers through Bruce's curls and his dick pressed hard into the mattress but there was an awkward, uncomfortable feeling welling up in the pit of his stomach that made him want to bury his face in the sheets and disappear rather than face whatever conversation was coming but –

But then Tony was there, next to him, easing him up and kissing him carefully, tasting Pepper on his lips, making him moan. And then Pepper's lips replaced Tony's as he nipped and scraped his way down Bruce's neck, throwing him back on the bed, sucking at his collarbone, Bruce's hips pressing up into Tony's body, needing the friction, his lust reignited, his dick painfully hard.

Tony unbuttoned his pants, carefully pulling them down with his boxers, low enough to let his dick out, and Pepper's fingers pulled up his shirt, running along his hips, causing his skin to prickle as she moved her lips to his ear, biting at it. Bruce wasn't used to this kind of attention and it took every ounce of his self-control to reign in the part of him that wanted to lose it.

The problem with his alter ego was that pleasure and pain were such a fine line. He wanted this, sure, but god – how many times had pleasure brought him pain? And how many times had pain brought him pleasure? It all merged together in his brain until his heart was pounding and his hands were sweaty and he tried to grab something, anything, as Tony went down on him and he groaned from beneath clenched teeth, slammed his eyes such, balled his fists in the sheets and tried to hold on.

Thankfully, Tony was good. Tony had done this before. Tony knew his particular parameters. In fact it was Tony who convinced him it was possible for him to have sex in the first place.

So he went slow, he set a pace for Bruce to breathe to, and Bruce's fingers loosened on the sheets a little, breathing deeply in time with Tony. Up, down – in, out. Pepper reached for his hand, lacing their fingers together, and he took a cautious glance up at her, a momentary jolt of guilt shooting through him as Bruce wasn't used to being the center of attention like this. The whole thing made me nervous and the fact that it was Pepper – right there, Pepper – who he'd spent months living in fear of, Pepper – right there, watching...

But she pushed her hair back behind her ear with her other hand and smiled down at him, squeezing his hand to reassure him before leaning down and kissing him. He focused on the feel of her lips on his and his heart rate and his breathing and Tony's warm, wet mouth and the increasing pace, the increasing suction, until he let it overwhelm him completely, drag him tumbling down into that place that was so much like pleasure, so much like pain, it wholly took his breath away.

Tony chuckled as he moved to lay up beside him, throwing a leg over Bruce's and reaching out to cradle the back of Pepper's head. Bruce watched through half-lidded eyes as they leaned over him and kissed, sharing a look he couldn't decipher as she pulled away, biting her lower lip in a grin. It almost felt like he was being left out of a joke, but he didn't care.

"You two are amazing," Tony enthused as Pepper laughed and Bruce frowned, wishing he could look away but surrounded by them on both sides he could only stare at the ceiling.

"Amazingly bad at making good decisions," Bruce muttered and closed his eyes and Tony laughed, jabbing at his side.

"Is he usually this pessimistic?" Pepper teased, pulling at a lock of his hair.

"Usually," Tony replied with a grin and Bruce shot him a glare, a scathing reply on the tip of his tongue but Pepper was sitting up and pulling her shirt out of her skirt, heading towards the bathroom.

"Unfortunately I have to shower and get to this meeting," she sighed, flipping her hair over her shoulder as she slipped into the bathroom.

Tony shot Bruce an apologetic look as he followed her, leaving Bruce there to stew in a litany of potential complications. What if she wasn't okay with it, now that it was over? What if she changed her mind? What if she hid how much it grossed her out to see Tony going down on him? What if she was going to jet back to California and then kick him out?

By the time Tony returned two minutes later he was halfway packed in his mind and ready to go but Tony stripped off his shirt and flopped down beside him, reaching for his hand and playing with his fingers.

"She's... okay?" Bruce asked, cautiously looking over at him and Tony nodded.

He didn't smile, but his face was relaxed, honest. It calmed the anxiety in Bruce to see it. It always did. It was the reason he had stayed here with him as long as he had.

"Yeah. She's a little embarrassed –"

"Embarrassed?" Bruce interrupted in concern, chest tight.

"Aren't you?" Tony asked honestly and Bruce frowned.

"More like mortified," he admitted and Tony exhaled a laugh.

"Don't be mortified. She's not – I mean, she's concerned it was a little fast but she's okay," Tony assured him. "She enjoyed it. You should let yourself enjoy it too."

Bruce snorted, only feeling so much relief. "And you?"

A lazy smile spread over his face as he closed his eyes. "What's not to want? We'll work out the details."

That left Bruce feeling even less reassured and as Tony's breath evened out before sleep, Bruce stared at the ceiling, listening to the shower, fretting about what he should or shouldn't do, should or shouldn't say, all of his fear of Pepper rushing back and threatening to overwhelm him like a tidal wave, crashing down to drown him.

But when she stepped out of the bathroom in a spare suit, hair still half wet but twisted into a professional bun, a quick application of eyeliner and lipstick. She glanced over at them on the bed, her lips quirking up in amusement before she leaned down to slip her heels back on.

"Oh yes, please, by all means, take a nap while I go out and run your company," she called over her shoulder and Bruce watched Tony's brows knit together in frustration, though he didn't open his eyes.

"Your company!" he called back and Bruce's eyes shifted back to Pepper, laughing and picking up her bag from the end table she left it on.

"Yeah – twelve percent of it," she answered, some inside joke between them, but they both chuckled.

It was weird, Bruce felt like an awkward third wheel, but it wasn't bad either, and Pepper paused on her way to the door, walking back to the bed. Bruce lifted himself up on one elbow, unsure of what she wanted but she just smiled at him gently, put her hand on his shoulder.

"Stay," she murmured, giving his shoulder a gentle pat before turning around and walking out as Bruce deflated into the bed.

The room was almost too quiet. Tony's gentle snore was the only sound and Bruce was left studying the room that had become comforting and familiar over the past few months – the bookcase of books he'd carefully collected, the warm beige paint that glowed in the afternoon light, the little circular table with ornate wingback chairs where sometimes they would eat breakfast, the few houseplants he managed to keep alive after rescuing them from Tony's "care."

And the thing was... this was his home, now. Whether he had ever intended it to be or not. And he decided, as his eyelids grew heavy and shut, that as long as he had Pepper's permission, he would stay.