Hyperdimension Neptunia is owned by Compile Heart, Idea Factory, Sega and whomever else worked on it.
"So, what is this place?" White Heart asked as she, her sisters, Green Heart, Yellow Heart and Purple Heart walked into a cave.
"A place that said that only people with substantial breasts could enter." Green Heart said with a giggle that caused White Heart to twitch in annoyance.
Purple Heart sighed and shook her head. "Specifically, the tablet inside apparently need three people with large breasts and three without them. Which is why I called P-Ko and you three to help Vert and I with this." She mentally sighed at White Heart's annoyed look. "If it makes you feel better, Blanc, I'll let you have first dibs at any treasure that you might find interesting for Lowee."
"But this is so cool!" White Sister Pink's blue eyes were sparkling as she looked around. "A whole new dungeon opens up and we're the first that get to enter."
"Could have asked C-Sha..." White Heart grumbled as the group stood in front of a large stone tablet with a green square on the top. Suddenly a beam came out of the gem and a chime sound was heard. The next thing anyone knew, something fell down and hit the floor with a bounce.
"...A treasure chest?" Green Heart asked as everyone walked up to it. "And such a stereotypical design as well. This was it? A cave that we thought was a dungeon is simply just an item spawn location?"
Purple Heart shrugged. "Perhaps it was designed by the Gods of old JRPGs or something?"
"Oh please," White Heart had a dour expression on her face, "we can animate the entire insides of our cities now instead of just using still background images, so why is it like this?"
White Sister Pink sweat-dropped and scratched her cheek. "Blanc's really mad if she's breaking the fourth wall."
"YAY! TREASURE!" Yellow Heart cheered and punched the lock, which broke it, and caused the chest to open up.
As the chest opened up, a bright light flooded the cavern and everyone had to cover their faces and turn away. When the light dimmed down, everyone lowered their hands and looked closely at what was inside.
"Nothing?!" White Heart yelled in frustration and threw her arms up. "I could have been writing some books and instead I have nothing!"
"Uh... Blanc..." White Sister Blue stared in shock. "Look! Boobs!"
"Huh?" White Heart blinked and looked down. To her shock, she had boobs! Huge ones! In fact, they looked like they were as big as Yellow Heart's boobs, but on her body!
"AHHHH!" Green Heart suddenly shrieked and everyone looked at her and stared in shock and horror as the CPU was patting her chest. "My boobs are gone!"
"Mine too!" Purple Heart gasped.
"Pea isn't bouncy!" Yellow Heart gasped.
"Oh cool! I have boobs now!" White Sister Pink cheered.
White Sister Blue was blushing and fidgeting. "I have boobs too... Nnngh..." She looked over her shoulder and realized that her new additions were causing her to have quite the wedgie.
"This is the most horrible thing ever!" Green Heart screamed in despair as she fell to her knees and started openly weeping. "My boobs! My beautiful boobs! They're gone!"
Purple Heart felt a headache coming on and put her pinkie fingers into her mouth and blew, catching everyone's attention with her whistling. "Listen! We need to get this chest back to Planeptune. I'm sure that Histy can figure out a way to reverse this."
"SCREW THAT!" White Heart yelled and ran up to Green Heart before swaying herself side to side, smacking Green Heart in the face with her giant boobs. "SUCKS THAT I HAVE BOOBS NOW, DOESN'T IT?! THIS IS FOR ALL THE TIMES YOU TEASED ME!"
Purple Heart rubbed her forehead as Yellow Heart grabbed White Heart and pulled her away from Green Heart. "Rom, Ram, can you take the chest and P-Ko, you take Blanc, I'll take Vert."
"Sure!" The twins said as they grabbed the chest and carried it out while Yellow Heart carried White Heart out, who was struggling and wanting to smack Green Heart's face a few more times.
"My boobs..." Green Heart sobbed.
"...Vert, if you get up and don't make me carry you back, I'll let you sleep in the same bed as Nepgear tonight."
Green Heart immediately stood up as though she was launched by a spring and started walking out. "Sleeping with Nepgear, but my boobs! She won't be able to use my boobs as a pillow. I want my boobs back. Waaaah!"
Purple Heart sweat-dropped and followed after them. "I really hope Histy can give us good news."
(-)
After returning to Planeptune and telling Histoire what happened, the book fairy nodded and began analyzing the chest.
"So..." Nepgear smiled at the CPUs, "why are you all still in HDD? Shouldn't you return to normal now?"
"I guess we can." Purple Heart nodded as everyone released their transformations.
"I STILL DON'T HAVE BOOBS!" Vert cried and Nepgear sweat-dropped heavily, especially as the Lowee trio still had their boobs. "It's not fair!"
"I know!" Rom's eyes sparkled and Ram grinned as she realized what her sister was up to. "Boobie hug!"
Everyone sweat-dropped as Rom and Ram hugged Vert on both sides, but made sure to smoosh her head between their breasts.
"You know, some people would love to have their heads squished by two pairs of boobs." Neptune commented and scratched her cheek.
"Don't care, I have boobs now!" Blanc huffed and crossed her arms under her breasts and smirked. "Now who's the flat one, bimbo heart?"
Vert started openly sobbing and the next thing Blanc knew, she was yelling in pain as she was lifted off the ground.
"Bad Blanny!" Peashy yelled as she lifted Blanc by her panties, giving the bigger CPU an atomic wedgie. "No teasing Beru Beru."
"I was about to say that we can all see Blanc's underwear, but I guess Peashy demonstrated for us." Nepgear giggled as Peashy let go, causing Blanc to turn around and yell at the tiny blonde, while chasing her around the room.
"I don't think Blanc cares that we can see her ass either." Neptune commented before wincing as Blanc couldn't see under her feet and tripped over a toy that Peashy had thrown behind her, causing her crash face-first into the floor and put her butt up high in the air. "You should probably fix that wedgie, Blanc! Your panties are on so tight that I can almost see a camel's toe."
"That's camel-toe, Neptune." Nepgear giggled nervously as Blanc stood up and tried to adjust her underwear, but was finding it hard to do so. "Hold on, Miss Blanc, I'll help."
"I want my boobies back." Vert sobbed while the twins sweat-dropped, glad they weren't wearing a dress that day.
(-)
Three hours later...
"Well, I have good news and bad news." Histoire said as she floated into the living room and tilted her head in confusion. "Why is Blanc tied to the wall and why is Vert sleeping on Rom?"
"Blanny was a big dummy head and knocked Beru Beru out with her big boobies!" Peashy protested.
Nepgear smiled nervously. "Blanc's been teasing Vert a lot since the boob thing and Vert shot back that at least Vert didn't need an accident to have actual boobs and then Blanc got mad and did a Tanzerin Trombe with her boobs and knocked Vert out."
"So, start with the good news!" Neptune popped in. "I want my HDD boobies back too!"
Histoire nodded. "Well, the good news, this is only temporary, there was a spell in the box that would swap breasts of three people with boobs to three people without boobs randomly. The bad news?"
"Three days?" Neptune, Nepgear and Peashy all asked and Histoire nodded.
"Yes, this effect will last for three days and... Blanc, do you know that your underwear is on full display for everyone to see?"
Groaning as she was tied to the wall, Blanc nodded. "Peashy gave me a hell of a wedgie, so yes, I know."
Rom whimpered. "Does this mean I need to let Miss Vert use me as a body pillow for three days?"
"No, Rom," Nepgear smiled and helped Rom get out from under Vert, who whimpered softly in her sleep. "Though, maybe you three want to stay here until it wears off? I'm not sure Lowee could handle you three showing up with big boobs."
"Can't we just use a needle and pop them?" Ram asked as she pulled out a long needle and gave Blanc a slightly crazed look. "We should pop the bad boobs on Blanc!"
"NO!" Blanc yelled as Ram started to creep closer with her eyes looking like diamonds. "Neptune! Help!"
Before Neptune could try to jump in, Ram jumped at Blanc and poked her boobs with the large needle.
"OWW! You little brat!" Blanc glared at her sister. "When I get free, I'm going to poke your boobs with that and see how you like it!"
Ram pouted as she pulled the needle out of Blanc's boobs. "They didn't go pop."
"You need to pop both of them." Rom said as she had another long needle and walked up to Ram.
Blanc's face went blue as her sisters suddenly started poking her boobs over and over with the long needles. "OWW!"
"Okay now." Purple Heart grabbed the twins before they poked Blanc more than ten times each. "No more of that or I'll shove eggplants into you where the sun doesn't shine."
"AHHH!" The twins yelled and ran off, well, bounced off, as they didn't want that.
Purple Heart sighed and let Blanc down. "Sorry about that, Blanc, but no more smacking Vert around with boobs."
"...Can I at least smother her?"
Purple Heart giggled. "I have a better idea."
(-)
Two hours later...
Vert groaned as she woke up and patted her chest, sobbing as she realized that she was still missing her boobs. "Oh boobie-o! Oh boobie-o! Where for art though, oh boobie-o?" She sat up and blinked as she saw something on the table. "What's this pamphlet?" Vert tilted her head to the side in confusion. "To everyone in Leanbox... What is this?"
Vert's eyes went white and blank in shock as she opened it up and there was an image of White Heart in nothing but an apron. Her large breasts were pressed against the fabric, stretching it out. "Wh-wh-whaaa?!"
Under the photo was one simple line...
"I have better boobs than Green Heart, you should come to Lowee and worship me."
"NOOOOOO!" Vert yelled as she stood up and tore up the pamphlet and transformed. "I don't care if I don't have boobs! My people still love me and..." She paused as she heard some laughing. "...What?"
"Bwahahahahahahah!" Both Neptune and Blanc fell out of the kitchen and into the living room while pressing their backs against each other and laughing. Behind them, giggling nervously, was Nepgear.
"Sorry, Vert, but my sister and Blanc played a prank on you."
"Oh really?" Green Heart narrowed her eyes at the laughing CPUs. "I guess I should thank them." She summoned her spear and both Blanc and Neptune's laughter slowly died out as they stood up and backed away.
"Um, Miss Vert, are you... Pissy?" Neptune asked nervously.
"Why no, Neptune. I'm not pissy." Green Heart had a serene smile on her face. "I just think I should show my friends how I feel. A good poke to the butt should help with that."
"AHH!" Both Blanc and Neptune yelled as they ran away from Vert, who was chasing them around.
Nepgear just giggled as she watched Green Heart chase Neptune and Blanc around, eventually managing to poke both of them in the butt so hard that the one she poked launched themselves straight into the ceiling. "Too bad Uni wasn't able to go with, it might be kind of neat to see Uni with big boobies."
And here I thought I was out of ideas.
So, saw an image on DeviantArt with Rom, Ram and Blanc with boobs and suddenly this came to me.
The artist is Caramel-Sheep if you want to see it.