How Using My Oppai Skill to Enlarge My Sister’s Breasts Led to Building a Harem - Chapter 11

Chapter 11

I’d gained a new fuckbuddy, Riria, and was juggling studies, the clinic, and sex in a busy daily routine.

(My crotch feels so good…)

In a dream, I was having sex with various women I’d been with. They appeared one after another, riding my cock, grinding their hips.

(What is this… where am I…? I don’t know, but it feels amazing.)

In a hazy, white void, I felt like I was in paradise.

But the dream couldn’t last forever. My consciousness slowly surfaced, sensations returning as I woke.

(I want to stay in this blissful world… my cock’s about to explode—ugh!)

Still half-asleep, an intense urge to cum hit me. A moment later, pleasure surged through my brain, so intense I let out a moan.

“Gu… haaa…”

“Good morning, Onii♪”

The girl addressing my pleasure-dazed self—

—was my beloved little sister, Ai.

“You came so much♪ Looked like it felt really good.”

Ai was in workout clothes, likely from her morning run.

“Sorry, seeing your hard morning wood got me all horny…”

“It felt incredible, Ai.”

“Ehehe♪ I love you, Onii. Chu♡”

Post-workout, Ai’s body was flushed and aroused, unable to resist my morning erection.

“But I’m all sweaty… you should shower.”

“Your sweat’s fine with me.”

“No way! Mom and Dad are at work, so let’s shower together♪”

“Then I’m in.”

To satisfy my still-raging cock, I decided to shower with Ai.

And so, another day began.

※

But trouble brewed at school…

A few days ago, I’d told Yukino about Riria becoming my fuckbuddy. Though shocked at first, Yukino trusted Riria’s promise to keep quiet, and they got along.

But during one lunch break, we went to the library storage for a threesome—

“What do you think? Riria said it’s stylish, so I tried it…”

“Haha, looks great, Yukino-cchi! Cute, cute♪”

Yukino, bra off, had huge rings on her ears and nipples.

“W-What’s that, Yukino? Those aren’t real, right…?”

“Haha♪ Fake piercings! But if Yukino-cchi likes them, I’ll introduce her to a piercing shop♪”

Relieved by Riria’s words, I froze, staring at Yukino’s body.

(She’s gotten so sexy… her breasts are bigger too…)

“Girls do this these days, right?”

“Yup, totally normal.”

“…”

Riria’s influence had transformed the earnest Yukino. At this rate, she might actually pierce her nipples without me knowing.

(No way… the serious Yukino, like this…?)

“You serious?”

“Yukino-cchi’s plain, so I’m teaching her stuff♪”

“Thanks, Riria-chan.”

No good. I instinctively knew Yukino’s trust in others and Riria’s sluttiness were a disastrous combo. Yukino could end up a full-on slut.

“I… liked the old Yukino better.”

“Huh…?”

“Ehh~?”

The Yukino I loved was serious, plain, intense but cute.

“But I’m so plain… Riria said I’d get dumped if I don’t change…”

“Riria… you.”

“What? Did I do something wrong?”

She meant well, which made it worse. Yukino trusted her because of it.

“You’re fine as you are, Yukino. You don’t need to change.”

“R-Really? What should I do…?”

“Don’t listen to Riria. Trust me, your boyfriend.”

“Y-Yeah, my boyfriend’s more important, right?”

Yukino trusts me, but as her “school-only” boyfriend, I felt guilty for causing her insecurity.

(Maybe I should explain things to Ai and the others for Yukino’s sake.)

“First, let’s deal with those rings before sex…”

I loosened the clamps squeezing her nipples, removing the rings. Fake piercings like these, screwed on tightly, block blood flow.

“Ah… ouch…”

“Poor thing. I’ll fix it right away.”

They might hurt if they rub. I gently licked her swollen nipples, soothing them.

Chururu, chu… chupa♡

“Hii♡ My nipples are tingling… ah♡”

“Don’t worry. Leave your breasts to me.”

My special ability kicked in. Sucking her nipples alternately, rubbing in saliva, seemed to boost internal healing.

“How’s that? Still hurt?”

“Nnu♡ Not at all anymore.”

“I’ll suck harder to increase blood flow. Juu… juchuu.”

“Ahaaa♡ That’s good♡”

Hearing her cute moans, I lovingly licked her nipples, easing the pain with pleasure.

“Wow, Yukino-cchi’s voice is too sexy…♡”

“Ah…♡ Any more, and I’ll come…!”

“Jururu! Come on! Rero, juppuuu…!”

Rolling her nipple with my tongue, teasing it, her body convulsed as pleasure peaked.

“Ah, I’m coming~~~! Haa…♡♡♡”

Yukino came from her nipples alone, gazing at me with a dreamy toron♡ expression.

“Hehe, you’re cutest as you are.”

“Ehh~ I wanna make her more stylish~”

I hugged Yukino, shielding her from Riria’s influence.

“Trust only me.”

“Okay♡”

“Good… now let’s fuck.”

Sucking her nipples had my cock at its limit.

“I’ll make you feel so good.”

Thus, Yukino escaped Riria’s clutches, though I didn’t realize it would deepen her dependence on me.

※

“To Yukino’s house now?”

“Yeah, is that okay?”

One day after school, Yukino invited me over. She’d never asked before, but I wasn’t opposed.

“Sure, no clinic appointments today.”

“Good…”

“What’s up? Why suddenly?”

“Um, my little sister… wants you to come over…”

Her sister. I knew Yukino had one, but why me? Still, I couldn’t refuse her request.

…

Yukino’s house, the Tsukihara residence, seemed affluent but normal.

(I braced myself since she’s Ayaka’s relative, but it’s pretty normal…)

“Something wrong?”

“Nah, nice house.”

“Really? I think it’s normal.”

Chatting, we entered.

“I’m home~ Oh, shoes here, so she’s back.”

“Your sister?”

What’s she like? Like Yukino, serious? A bit excited, I followed Yukino to the living room, where—

“Hey! You’re the guy who seduced Yuki-nee!!”

“Whoa!?”

A sudden shout nearly knocked me off my feet.

“Hey, Nao, stop it!”

“Stay out of this, Yuki-nee. You tricked pure Yuki-nee and taught her lewd stuff, didn’t you!?”

“Whoa!? That’s dangerous!”

Yukino’s sister (Nao-chan?) grabbed my collar, shaking me. Tall for a girl, strong, she rattled my head back and forth.

“Nao!! Stop!”

Paschin! Yukino smacked Nao’s head.

“Yuki-nee… I’m doing this for you…”

“No violence! I’ve told you! Sit down.”

“Quite the lively sister, Yukino…”

I ignored Yukino’s smack.

“Hmph! Brainwashed Yuki-nee, you pervert?”

Talk about harsh. I sat across from Nao to talk.

“First, tell me why you’re mad.”

“Why!? Yuki-nee wanting piercings is your fault!”

As expected. I bore some responsibility, so I couldn’t deny it.

“Nao, my friend said they’re stylish.”

“No way! Yuki-nee never had friends before!”

Ouch, that’s a tough one to counter.

“I made one recently! Riria-chan meant no harm.”

True, no malice—just a lack of common sense.

“But… your boyfriend’s this flashy guy, right?”

“Yup. Cool, huh?”

“That’s why I don’t trust him!”

Nao glared, ready to bite. Struggling to respond, Yukino stepped in.

“Nao, you know about Ayaka-oneechan’s illness, right?”

“Yeah, she’s cured…”

“He’s the one who cured her.”

“What!?”

Being sisters, Nao was naturally Ayaka’s relative too.

“I wouldn’t lie, right?”

“Well… yeah, but… Ayaka-nee’s savior… ugh.”

Even I felt offended by her reluctant face.

“Ayaka-san helps at my clinic. I’m grateful.”

“So… it’s true…?”

Finally believing, I explained the nipple piercing issue.

“Sorry, I misunderstood!”

“It’s fine if you get it.”

The tense air cleared, but Nao’s interest shifted.

“So… you and Yuki-nee… have sex, right?”

“Nao…!”

“It’s normal for couples, right?”

No guy wouldn’t, so no need to hide it.

“R-Really… wow…”

Nao, curious about sex, kept asking about our physical relationship.

(She’s in eighth grade… well-developed, maybe horny too?)

Yukino’s insanely lustful. It wouldn’t be surprising if her sister was too.

“You did it in the bathroom…?”

“Nao, enough already.”

“C’mon, Yukino, eighth graders are at their horniest, right?”

“N-No way!?”

Nao loves dirty talk but panics when it’s about her, like a middle school boy. I couldn’t help laughing.

“Hey, Onii-san, don’t laugh…”

“Onii-san?”

“If you marry Yuki-nee, you’ll be my brother-in-law, right?”

“…”

I hadn’t explained Yukino isn’t my main girlfriend. Would Nao accept that, or would her earlier ferocity return? Cold sweat ran down my back.

“Nao, relationships are complicated.”

“What, Yuki-nee?”

Yukino explained I have another girlfriend, and she’s my school-only second girlfriend.

“That’s… allowed?”

“If we’re okay with it, it’s fine, right?”

“Umm…”

“Kids like Nao might not get it.”

Yukino smirked, acting superior. It was endearing.

“I’m not a kid! My breasts were bigger than Yuki-nee’s before!”

“Mine are bigger now.”

Thanks to my daily massages. Yukino didn’t ask for it, but I unconsciously shaped them to my taste.

“Want me to make yours bigger, Nao?”

At her age, she’d care about looking pretty.

“B-Bigger… my breasts?”

“Yup. Massages can make them grow.”

With Yukino as proof, Nao compared their breasts.

“Just breasts… okay, please…”

Thus, I ended up massaging Yukino’s sister Nao’s breasts.

…

“Lie on the bed.”

With Yukino watching, I had Nao lie on her bed in her room.

(More girly than I expected…)

Nao’s room was pink, adorned with cute trinkets and stuffed animals, very feminine.

(She yelled at first, so I thought she was aggressive, but she’s a normal girl?)

I observed Nao, slightly nervous. Pink-dyed hair, fierce eyes, well-developed for a middle schooler—tall, almost my height, with large breasts. Her body was well-proportioned.

Time to switch to work mode.

“I’ll open your top.”

“Ah… uh.”

With practiced ease, I unbuttoned her blouse, removed her bra, and neatly folded it beside her. I’m practically an artisan at undressing.

Nao’s youthful breasts were perky, like perfect white peaches.

“I’ll apply oil. It’s a bit cold.”

“Hya!”

I chose slick oil for beginners, dripping it onto her nipples. Her unpigmented, pink nipples were pristine.

(Not much experience, huh.)

I delayed stimulating massage, starting with acupoints at the breast base.

“Tell me if it hurts.”

“U-Un—Hau!?”

I didn’t press hard, but it might’ve been intense for Nao. Just sinking my fingers into the meridians from her armpit to her breasts made her jolt and writhe.

Gu… Guku, munyu♡

I moved from her armpit to the breast base, the mountain’s foothills.

“Kuu… haa, nnu…♡”

Her pleasure nerves activated, her breathing quickened, mixing with sweet moans.

“Nao-chan, feel this? These are connected.”

I traced from her armpit to mid-breast.

“Hiuuu…!?”

“So, pressing like this!”

(Nao’s young, so her Cooper’s ligaments aren’t stretched. To enlarge, start from below.)

I began pressing from her underbust.

Munyu♡ Munyumunyu♡ Gu! Gyuu♡

“Hiii♡ My breasts are hot~”

“That’s blood flow increasing.”

“Oh♡ Oh—… Ohhh~~~♡”

Using all ten fingers freely, I stimulated acupoints, and Nao started making cute noises.

“Nao, your voice is loud.”

“S-Sorry… I can’t help it… haun♡”

My ten fingers sank into her breast’s erogenous zones, a technique to block meridians, enhancing massage effects.

“Huh? It stopped…”

“Here we go, Nao-chan.”

Releasing my fingers, I unblocked the meridians, grabbing her breasts, gunyuri♡, and lightly shaking them side to side.

“Nha, aaa… what? Something’s coming…!”

“No need to hold back your voice.”

Knowing restraint was bad, I shook her hypersensitive breasts side to side.

Puru♡ Purupurupuru♡♡♡

“Ohu♡ Ohhh~~~♡♡♡”

E

Funyu♡ Funifuni♡ Munyu♡

“Nghiii♡ My breasts, no! S-Stop~~~♡”

“Stopping will make it last longer.”

“Niii♡ No way…! Ohhh~~~♡♡♡”

Nao let out beastly moans, convulsing. The intense pleasure likely overwhelmed her brain, numbing her rationality.

“Let’s finish.”

Using my palms and fingers stickily, I kneaded her sensitive breasts like dough.

Munyumunyu♡ Munyumunyu♡ Kunyukunya♡♡♡

“Ohh♡ I said… no more… naa♡ Aa… no, something big, it’s coming~~~”

“Push past it, and you’ll feel better.”

“Ah♡ Ah♡ Ah♡ It’s here, here~~~ Nghiiii~~~♡ Oh…~~~♡”

Nao arched on the bed, toes pointed, like she’d been shocked, eyes half-rolled, drooling.

Her lower half made wet sounds, soaking her panties, a sweet girlish scent filling the air.

“You’re okay, Nao-chan. Take it slow to calm down.”

“Hoo♡ Nhoo♡ —Nha…♡♡♡”

For aftercare, I gently massaged her breasts in circles.

“Feeling calmer?”

“Y-Yes… my head’s all white…”

“Worked well, huh.”

Reluctantly, I let go of her soft breasts, which jiggled, purun♡, with better color than before.

“Good job. Different from the clinic, right?”

“She’s growing, so I avoided hindering development.”

Her young breasts have growth potential. I explained to Yukino I used a method to enhance their natural quality.

“A few more sessions, and they’ll be perfectly beautiful.”

“S-So… I have to do this multiple times?”

Nao sounded shocked, her speech slurred.

“One session should show a difference.”

I’d miss rubbing such a cute girl’s breasts, but if she didn’t want it, I wouldn’t push.

“If you want more, just say. Anytime.”

I left it to her, avoiding pressure.

But the problem was—

“Look, it’s huge♡”

“Hey, Yukino!”

“Let’s go to my room. Mom’ll be back soon.”

What else but that?

…

“Ah♡ Ah♡ Ah♡ So good♡ Feels like real lovers♡”

“Your bed smells like you, Yukino.”

“That’s embarrassing♡”

To calm my raging cock, I started fucking Yukino on her daily-used bed.

Paan♡ Panpan♡ Pampampan♡ — Pan!!

“Aan♡ The bed’s breaking♡ Aaahiii♡♡♡”

“Fu… fufu. Smells so good… my cock’s rock-hard, can’t stop my hips.”

“Faa♡ Thrust harder… break it~~~♡♡♡”

Excited to fuck outside school, we got carried away.

Unaware of a girl in the next room, ear to the wall, masturbating furiously…