Chris grows a large pair of breasts

"Oh no, I'm so sorry!" Emily says, trying and failing not to laugh as she catches her breath. Her face is bright red in embarrassment.

Chris begins to carefully take off his shirt. It's completely soaked through and already sticking to his chest. "That's okay, it happens." He says, his face is also bright red.

As he takes off his shirt Emily notices that he's wearing a binder. "How long since you got infected?" She asks spontaneously.

"Uhh, over a year." Chris answers, checking his binder for stains. "Long enough for my ovaries to grow me a little pair of tits." He adds awkwardly as he starts to remove the cum stained binder.

His breasts are small and hairless with a slightly conical shape. Emily can't help but notice that his nipples are fully hard, sticking out over a centimeter, each as wide as a AA battery. She notices him looking her way, and tries not to stare, but something catches her attention.

"Chris, your boobs." She says in surprise. "It looks like they're growing!"

Chris looks down just in time to see his chest start to swell. "Oh fuck..." He says, anticipating more of the pain he felt as they first grew in, but instead of pain it feels incredible. "Oh... fuck..." He groans slowly.

"Do you need painkillers?" Emily asks, grabbing the syringe, but Chris shakes his head no.

Chris pants and gasps as his breasts begin to grow in earnest. As the nanobots fill his breasts with fat, they pull mass from other areas, causing his shoulders and waist to slim while his tummy is pulled flat. "Holy shit." He gasps in ecstasy. "I don't know why this is happening, but it feels amazing." He moans as his pussy starts to throb and tingle.

Emily watches in shock. She wasn't expecting anything like this. Almost more surprising to her than the transformation is how Chris seems so okay with it. "Are you okay?" She asks nervously.

"Yeah, yeah, I think so." Chris sighs as his transformation concludes. He's left with large breasts, significantly larger than Emily's. "It must have triggered a reaction with the dormant nanobots in my skin." He speculates.

"Oh, like with the rats. The attempts to reverse the nano-virus causes a counter reaction. There must have been copies of the virus we made in my ejaculate." She reckons as Chris nods along. "Are you sure you're okay?" She asks him seriously.

"Yeah, I'll be fine." He says, trying to sound casual. "What's a pair of tits in the pursuit of science?"

"Alright, if you're sure. But we could work on an antidote tomorrow if they bother you." She assures him.

"Emily, you've been working on an antidote to the original virus for years. Your dick is the closest we've got. Celebrate the breakthrough and keep going, don't worry about me." He says, looking down and sighing softly. "They were already getting bigger, part of me is glad I could get it over with all at once." He says as he stares at his transformed chest. "Plus, I think they look hot." He admits, shamelessly admiring himself.