A full shopping spree later you decided to go visit your girlfriend after a few days of just camping and waiting out for some magic stuff. In the nice and spacious living room you had a backpack full of stuff to share, and a pocket full of boob tube. Your girlfriend wasn't that busty, but tried to act sexy and asked "Is that a magic wand in your pocket or is it just me?"
"ha ha..." you "laughed" and then said "Not a wand. More of a weird non-lethal weapon of sorts."
Your girlfriend looked a little shocked "You bought a weapon?"
You took it out and said "Well... It's not harmful... least directly. They called it a boob tube with a surprise and immobility option."
"What does it shoot boobs or something?"
"No it grows boobs actually. Only lasts an hour though."
Your girlfriend looked at it and asked "I'm curious. Can I get a shot of the surprise?" You took out the boob tube, made sure the option was on surprise, and then aimed at your girlfriend who was right next to you and fired. You had imagined it was more of a gun instead of a grenade launcher, but when you fired the boob tube you saw something spherical shoot out for a split second until it made contact with your girlfriend and burst. There was a smokescreen that came out that you both were coughing through. You had to remember to use that to make an escape and not cough, but once the smokescreen clear you could feel a tightness in your chest. You could feel it tingle as chest hairs withdrew, your areola widened, nipples lengthened, and chest grew into A-cup boobs stretching out your shirt.
"Ugh, I was in the blast radius..." you muttered
"Woah are those real?" Your girlfriend asked leaning to look at your chest unthinking about her breasts starting to spill a bit out of her somewhat tight neckline and bra. As she started groping you a little you muttered a bit as you felt their sensitivity. "It only lasts an hour right? Let's go further!"
As she tried to get the boob tube from you you tried to resist and say "No, this thing isn't some toy."
Your girlfriend tried knocking you down on the couch as she tried tickling you with one hand and snatch the boob tube with the other "This is totally a toy with other functionality, but let's play!" You continued resisting as she got further and further close to snatching the boob tube away. You both struggled and no one noticed as the switch got flicked to immobile and then the trigger was pulled. You felt the projectile hit your cheek, and disappear. However you knew what was about to come and pushed your girlfriend off of you as you tried to lay down a bit.
"Get on your stomach!" you yelled as you felt your boobs grow larger and larger swelling.
"How? My boobs make that impossible!" Your girlfriend said unhelpfully as her breasts were about the size of bean bags.
"This is what we get for struggling with a weapon" You said as both of your breasts were sofa sized and then a few moments later your breasts were both car sized.
"How was I supposed to know immobile meant this?"
"What did you think a boob growing gun with an immobile function meant?!?"
"Well... do you have anything in that bag that could maybe help us out?"