Hyperdimension Neptunia is owned by Compile Heart, Idea Factory, Sega and whomever else worked on it.

Read a comment online about Compa's grandpa and it inspired this.

Walking around Planeptune City, Uzume smiled as she took in the sights. "Man, the city sure has come a long way." She said to herself. Normally she went out with Nepgear or one of the two Neptunes, but the smaller Neptune had run off to Lowee to help Blanc with something while Nepgear was in Lastation visiting Uni. Uzume shook her head as she thought about the other Neptune, who had angered Croire with some sort of remark and ended up being teleported into a window where she got stuck and had her butt out on display for every pervert to look at for hours. "I love ya, Nepsy, but you are an idiot."

At least the dark-skinned fairy had enough decency to only humiliate Neptune by putting her on a floor high enough that people could see but not get to very easily. "And she's been staying in the Basilicom for the past few days." Not that Uzume blamed her friend. It was one thing to strip naked and run through the streets of Planeptune naked like Uzume did from time to time. It was something else when you weren't planning on exposing yourself to everyone.

"Though, I swear, there's someone who's been following me when I go streak-OH! Compsy!" Uzume's train of thought ended when she saw the busty strawberry-blonde girl with a basket in her hand. "Going on a picnic?"

"Hmm?" Compa turned to see Uzume jogging up to her. "Ah! Uzume." She smiled at the redhead. "I was going to go visit my grandpa."

Uzume blinked a few times before her eyes widened and she gasped. "Oh! Gearsy told me about some of the silly quotes your grandpa had."

Compa giggled at Uzume. "He's a nice guy, but I don't want him meeting my friends." She looked a little troubled and nodded. "See, grandpa is a pervert and he likes to feel a girl's boobies or their butt."

"Uh..." Uzume had a nervous look on her face. "He doesn't do that to you, does he?"

"Of course not, silly." Compa smiled at Uzume, who sighed in relief. "He raised me. But I worry he'd go crazy if he saw Nep Nep in her Goddess form or he saw Ge Ge or any other CPU. Well, except Rom and Ram, he's really kind to children." Compa's smile slipped from her face and she sighed. "But he's getting really old. He's not as energetic as he once was and I'm worried he's about to die." She held up her basket. "So I thought I'd bring him some of my home cooking."

"That's nice of you." Uzume smiled at Compa. "Hey, um, I don't suppose I can come with you?" Compa looked at her in confusion and Uzume rubbed the back of her head. "Well, if he's your grandfather and kind of old, he might know me. It would be kind of neat to meet some more people that remember me."

"Well..." Compa scratched her cheek. "Okay. But don't say I didn't warn you about him."

"It's fine." Uzume shook her head. "I'm a big girl, I'm sure I can slap away a hand without hurting him."

(-)

It was over twenty minutes later when Uzume and Compa found themselves on the edge of the city walking to a small, one story house that was painted light green and white. There wasn't much of a front yard, though Uzume could see that the front yard went along the South side of the house extending to a large open back yard while a small dirt path went along the North side. "This is..."

Compa smiled at Uzume. "Grandpa raised me here, he didn't have a lot of money, but we made due. I wanted to help grandpa move out of here, but he likes living here." She walked up to the door and knocked on it. "Grandpa! Are you here?" She called out while opening the door.

"Is that you, Compa?" A voice that was old and a bit high pitched spoke up as the two entered the house. "Oh, it does this old man's heart well to see you again." The voice cackled and Uzume looked around, wondering where the voice was coming from. "Hmm? Your friend?"

"Grandpa!" Compa smiled and walked over to a chair in the corner and that was when Uzume finally saw Compa's grandfather.

He was... Tiny. Even smaller than Histoire, which wasn't something that Uzume thought was possible. He was completely bald, except for some loose strands of hair on the sides of his head. But what threw her off was how his skin looked very thin and pale, almost like he was a living corpse.

For some reason, he was looking at her and his eyes got huge as he looked at her. "Isn't it enough that you used that banishment scroll that sent me to this world thirty years ago?!" He yelled at Uzume while pointing a finger at her and standing on the chair. For a moment it felt like he was being surrounded by energy and it was making him much, much larger than his actual size. "Have you come to finish me off? Well, I hope you've kept your training up, you blasted whelp! I won't..."

"GRANDPA!" Compa yelled and hugged the old man, causing him to falter. "Grandpa! That's not anyone you know. She's no manipulative bitch or son of a bitch who won't let you have your fun. Her name's Uzume. She's the former CPU of Planeptune."

The man blinked a few times and tilted his head in confusion. "Hmm... I don't know, are you sure that you're not the same person?"

"I've... Never met you until today." Uzume pointed out, though she remained tense, remembering that feeling that the old man had put out. "...What... What was it that you did there? It felt like you were getting really huge for a moment there."

"Hmm..." The man narrowed his eyes and sighed as Compa let go of him. "I see, my eyesight's getting worse, it seems, even with so many cute girls around to help this old man through his final years." He bowed to Uzume. "Please forgive this old man."

"Hey, it's okay." Uzume smiled at him. "It was just a case of you thinking I was someone who wronged you."

The old man nodded. "Yes, but you're taller than she was and you have two braids, but you're a redhead like she was and your boobs are about the same size."

Both Uzume and Compa sweat-dropped at hearing that.

"Dear..." The old man looked at Uzume and gave her a tearful look. "Can... Can you let this old man have some fun to apologize to you?"

"Uh..." Uzume scratched the back of her head in confusion and wondered why Compa looked kind of stiff in surprise. "...I guess you can, but why..?"

"SWEETO!" The old man suddenly yelled and despite his frail looks, he jumped at Uzume so hard that she found herself frozen in place as he planted himself against her chest. "Ahhhh! So nice! So soft and so pleasant!"

"What the hell?!" Uzume yelled, her face red as she, out of reflex, tried to punch the old man on her chest, but found he wasn't there anymore. "What the?" She stiffened as she felt hands on her butt with a face rubbing against her butt-cheeks. "The hell!?"

"Mmm! You're bigger down here than she was, but you're about as firm as she was." The old man complimented Uzume as he nuzzled her right butt-cheek. "Mmm! You must work out a lot. Lots of kicks?"

"GET OFF MY ASS!" Uzume screamed as she spun around while trying to get at the old man, but found it hard as he suddenly wasn't on her butt anymore. "AHHH!" Uzume screamed, her face bright red. "GET OUT OF MY SHORTS!" She screamed and shook her legs as the old man literally crawled around inside her shorts. Thankfully for Uzume, the man didn't have a good grip anywhere and quickly fell out of her shorts and onto the floor.

"Aww... That was too short." The old man sighed. The next thing he knew, Uzume was smashing her fist into the top of his head. "Owwies!" The old man cried out as he was punched into the floor. "That hurt!" He teared up as he looked at Uzume. "I thought a Goddess was supposed to be kind."

Uzume's face was bright red as she crossed her arms over her chest and jumped back. "Not if you're sexually harassing me!"

"Uzume!" Compa got in front of the redhead and gave her a pleading look. "Please! Grandpa Happosai didn't mean any harm. He has to steal women's underwear and fondle boobies to survive."

Uzume gave her a perplexed look. "...What?"

"I'm almost three hundred and fifty years old." Happosai said as he pulled out a pipe and took a small puff of it. "Being a human makes it hard to live that long without making some sort of sacrifice. I never tried to go after you CPUs." He smiled at Compa. "Compa here is such an angel. Found her when she was a baby and raised her as my own."

"Aww, grandpa, I love you too." Compa smiled and picked up Happosai, hugging him to her chest. "But you have to be nice to other girls too. It's why I won't let you meet Iffy, Nep Nep or Ge Ge, okay?"

Happosai pouted and nodded. "Okay." He then grinned at her. "So... When are you going to have children? I'd like to see your cute children so I can say I have some great-grandkids to spoil before I die for good."

Compa blushed at hearing that. "Oh, grandpa. I'm still trying to be a good nurse."

"Well, hurry it up." Happosai smiled at her. "You're only young once."

Uzume just shook her head. "I think I'll just wait outside, okay?" She turned and walked towards the door.

"Before you go..." Happosai spoke up and Uzume turned her head to look at him. "I just have one thing to say." Uzume tilted her head in confusion. "SWEETO!"

"AHHH!" Uzume screamed as Happosai seemingly teleported into her dress shirt and started crawling around on her breasts directly.

"No bra?" Happosai asked, almost disappointed. "I'll have to let you look through my collection of silky darlings, a cute girl like you shouldn't have to worry about your boobies sagging as you get older."

"GET OFF OF ME!" Uzume screamed as she struggled to remove Happosai from her body.

By the time that she and Compa got him off of her, she was sitting on the floor, naked except for her shoes, as Happosai rubbed her orange panties against his face.

"Ahhh!" Happosai sighed in relief from his chair. "A goddess's panties. So nice."

Uzume growled as she picked up her clothes and handed them to Compa. "I'm heading back home."

"...Like that?" Compa and Happosai asked in surprise.

"Not the first time I ran naked through the streets." Uzume said as she ran off before either of them could stop her.

"...Oh!" Happosai's eyes widened in surprise. "I thought I saw a streaker running through the streets, but I had no clue it was her."

Compa sighed and held out her hand. "Grandpa, gimme Uzume's panties so I can wash them."

Happosai pouted at her. "...Can I keep them for a week?"

"Grandpa, if you don't give them back to me, then I won't let you have the yummy food I made for you." Compa said and a moment later, the orange panties were in Compa's hand. "Thank you, grandpa."

Happosai smiled at her. "You're a good girl. You're going to make someone very happy in the future."

Compa smiled at him.

I ended it there, since this could have gone on for a long time.

Happosai is from the anime/manga series "Ranma 1/2". He's a pervert that makes Jiraiya look like a celibate monk. And, yes, he needs to grope women's boobs and butts and steal their bras and panties to survive.

...Suddenly Compa's weirdness makes a lot more sense.

And yes, Uzume is canonically a nudist who has no problem being naked, she just doesn't like people watching her get naked.