[Have to begin by giving a thanks to paisley15 for the suggestion of this fic! I'd been feeling guilty for not writing Science Boyfriends for a while, so now I feel better! This fic was what I needed!]

It was extremely impressive, that suit. Bruce had seen many of Tony's designs in the few months they had been working together—Tony would always call them "Science Partners forever," mostly as an excuse to force Bruce to do experiments with him—but this one was especially nice. Tony was busy showing off his new design on a screen JARVIS just pulled up. Apparently, he had programmed it to react on instinct if something dangerous got too close and Tony didn't already see it.

That, and he had played around with the color, picking a slightly darker red instead of the usual bright kind he used. It made it seem more deadly, probably because it was. Bruce was definitely impressed with this one.

"It's amazing," he said as Tony had a missile fly at the suit in the simulation.

"You think so?" The suit spun around as he said that, firing at it and making it explode. Smirking to himself, he added, "It definitely can be improved, but-"

"No," Bruce interrupted, his eyes still focused completely on the digital suit. Despite it still being on the screen—and not built yet—he was in awe of how it worked, and how calm he was around the real thing. Even the Hulk didn't get angry around it, despite it technically being a weapon. That still baffled him. "It's definitely the best design you've created to date. Even the change in color is incredible. It makes it seem more powerful, more deadly."

For a moment, Tony flinched, and the doctor instantly opened his mouth to defend him, to say he didn't mean it that way, but Tony waved it off. "No biggie, I got what you meant," he responded, leaning back over the computer screen. "I'm glad you think it's so great. There's still room for improvement though."

"There's always room for improvement," he responded, coming to sit down next to his best friend. "But, for right now, it's the closest you've ever gotten to perfecting your Iron Man suit."

Tony turned to look at him, an unfamiliar glint in his eyes, one that Bruce had never seen directed at anyone before. The genius slowly turned, turning his whole body until he was facing Bruce. It wasn't until THAT moment that Bruce caught on to what Tony wanted.

His heart thumped a little harder, and he had to remind himself to remain calm, because yes, this was what he had been wanting since the day he had met the man, and he had to not make a fool out of himself.

Of course, being genetically ruined, it was his destiny for such a thing to happen.

Tony leaned in, placing a gentle kiss on his lips, Bruce responding quickly by kissing him back. It was what he wanted, it was what he had always wanted. He'd never had this chemistry with anyone, not with anyone before or after he became a monster, not even with Betty. It was Tony Stark he wanted.

But, as the kiss intensified—his hands gripping the back of Tony's shirt and Tony's hands tightening in his hair—he suddenly remembered who he was, and what would happen after his heartbeat intensified. Regretfully, he broke the kiss, and started to push Tony away.

He couldn't have this, not as long as the Hulk remained inside of him and kept control over him. That thought almost made him want to cry.

"What the hell was THAT for?!" Tony demanded, hurt encompassing his brown eyes. Surprised, Bruce watched as tears began to form in his eyelids.

Regretting even allowing for Tony to kiss him—apparently it had meant a lot to the playboy too, which made his heart break, because he could finally have him, but the Hulk would ruin it within seconds—he muttered, "Tony, the Other Guy will kill you."

Angry now, he practically shouted, "Everything is about the Hulk with you! Maybe he'd be okay with us! Have you even bothered asking him?!"

"You don't just ask the Other Guy," Bruce responded, his voice louder but almost even, almost calm. Oh, if only his heart felt the same as his voice. "He'll destroy you. He destroys everyone who I try to get close to."

There were now hands on his face, Tony's hands, and they were pulling their heads together. He could feel Tony trembling, and he had to bite his lip to not start crying. He hadn't wanted to do this, not to Tony. But, it was necessary; it was necessary if he wanted to keep the only person he truly loved alive.

"What if I want to risk it?" Tony asked, his tone raspy and begging. "What if the Hulk likes me?"

Oh god. He hadn't wanted to do this, but here he was, telling Tony no. "He likes nobody, Tony. Nobody. Do you understand?"

There was desperation in Tony's voice when he responded, making Bruce's heart shatter like glass being rolled over by a car. "I don't want anybody else Bruce. Don't you understand?"

When Tony spun his question around, directed it at him, he felt his breath catch, his chest ache more than anything. He could feel the emotions riling up the Other Guy; he could feel him in the back of his head, becoming restless and wanting to take over. Taking in a deep breath, closing his eyes before he spoke and mentally hoping his best friend, his only love, wouldn't hate him forever, he said, "Tony, I don't want anyone else either. But... I don't think I could live with myself if I killed you."

Unable to take it anymore, he pushed past his fellow lab partner, his Science Partner, quickly striding out of the lab and into his bedroom.

"Bruce, can I come in?" The small voice of Pepper came from the other side of his bedroom door, and he hesitated, unsure of whether he should let her in or not. Sure, Pepper's company was very enjoyable; her usually-chipper attitude and positive smile made it easy to deal with all of the Avengers and S.H.I.E.L.D. chaos that went on with his life. But, she was also super close to Tony—despite them breaking up a month ago—and was probably here to defend him.

Still, it was Pepper. Sighing loudly, he said, "Okay, go ahead," and walked toward the wall, facing it so his back was to her when she entered.

He could practically hear her hesitating, her footsteps refusing to move from the doorstep for a little while before she finally did. "I heard about what happened. I'm... He really cares about you, Bruce."

"I know," he breathed into the wall, closing his eyes. He really didn't want to be having this conversation, not with how close he'd gotten to accidentally letting the big guy loose in his room a few minutes after he entered it. That had been one of the worst fight's he's had with the Other Guy, and he completely believed that it was because of Tony.

"Sometimes, I don't think he realizes how much of a risk he takes with some of the idiotic things he does," Pepper commented, coming to stand behind Bruce and put her hand on his shoulder. As he nodded in agreement, she added, "But, I think he's not being stupid in this case."

Surprised, Bruce turned around to stare at her, horror coming over his face. "Pepper, I'll kill him," he said, his voice trembling. "I don't think I could live with myself if that happened. Actually, I know I can't live without him." He could feel his hands trembling, and he had to form them into fists and keep them at his side in order to not punch the wall. "I just can't... I have no world without him, Pepper."

Confidently, she instead informed him, "The Hulk won't kill Tony, Bruce."

As the doctor stared at her, extremely confused as to where this confidence came from, the television Tony had provided him turned on, blank for a moment before footage of something came up on the screen. It took a moment, but when he realized what it was, a chill went over his bones.

It was from the battle against Loki and the Chitauri; the wreckage was evidence enough. Steve and Thor were standing in the middle of it, staring up at the sky. Up in the corner, he could see a huge green creature: him. Or, rather, the Hulk.

"What is this, Pepper?" he asked, his voice exhausted.

Putting her hands on her hips, she responded, "This was footage S.H.I.E.L.D. confiscated from a teenage girl who happened to be at the location where Iron Man touched down."

Of course. That made sense. The three of them had been close by when Tony came crashing down after his suicide mission. They really didn't talk about it much, but he knew enough to understand what was going to happen. Tony, crashing down onto the ground, probably somehow surviving because of his suit.

"I don't think I want to watch this," he whispered hoarsely, but JARVIS had already started playing it.

JARVIS had paused the footage at the exact moment that Tony had come back into the atmosphere, so the girl tilted up her camera and started to film Tony crashing down. All the while, she babbled about how close she was to superheroes, not even worrying about the fact that Tony might die. If Bruce had been there... well, Bruce would have fainted, had he been conscious.

Instead, the Other Guy had been the only one of the two to witness this event.

The girl panned down for just a second, enough to capture Thor swinging his hammer, but she let out a sudden cry, moving it back up...

... just in time to film the Other Guy saving Tony.

Now his hands were trembling, and they wouldn't stop. He didn't even want for them to stop. He saved Tony. The Hulk had saved Tony. As the Other Guy landed, protectively rolling over to save his friend from the impact, his legs crumbled a little, forcing him to sit on the bed. All his mind could think was, "He saved Tony, he saved Tony, he saved Tony."

"Do you see now?" Pepper asked as the footage suddenly stopped. "She quit filming at that point, when she dropped her phone, but Steve told me the Hulk shouted to wake him up from unconsciousness. He cares, Bruce. You might not think that possible, but it's the truth."

Completely in awe—his mind couldn't make up anything to say, anything intelligent enough to respond to this—he murmured, "He never saves anyone..."

"But he saved Tony," she said softly, her smile lighting up the room. "Does that change things?"

Now he had no words. Instead, he nodded his head, so slight she could barely see. But, she did. "Good," she responded. Then, turning her head to the door, she bellowed, "Tony, get in here!"

And, sure enough, in walked the genius billionaire playboy philanthropist that the Other Guy cared for, that Bruce loved. Not even caring that someone else was in the room, he scrambled to his feet, practically tackling Tony in a hug, and pulling their faces together into a kiss.

In the back of his head, he felt a rumble of approval, the Other Guy's approval. Bruce couldn't help but smile.