How Using My Oppai Skill to Enlarge My Sister’s Breasts Led to Building a Harem - Chapter 19

Chapter 19

I ended up in a physical relationship with Nao, the younger sister of my second girlfriend, Yukino.

Nao calls me “Onii-chan” and clings to me sweetly—and today, she’s at the clinic again.

“Hey, Onii-chan… wanna have sex again?♪”

“…Alright, I’ll put on a condom.”

“Ehh, can’t you just pull out like last time?”

“No way. I might finish inside.”

I can’t risk getting Nao pregnant, so we need condoms until her pill kicks in.

“The pill takes effect after the eighth day, so be patient until then.”

“Hmm, okay then! Oh, I’ll put it on for you!”

It’s her first time with a condom, so I guide her carefully.

“Squeeze the tip to remove air—yeah, good job.”

“Your thing’s twitching…♡”

“Your hands feel good, Nao.”

“Ehehe♪”

Nao beams, proud of putting it on correctly.

“Alright, time to pamper you plenty.”

“Ehehe~ I love you, Onii-chan!”

“Spread your legs.”

“Un… It’s still embarrassing to show you down there…”

Nao only lost her virginity recently and lacks experience. As her “Onii-chan,” I need to teach her.

“We gotta get you wet, or your pussy might hurt.”

“It’s fine… I’m already wet.”

“Wow, you’re dripping with naughty juices.”

“Ugh~ It’s ‘cause looking at your… cock makes my tummy hot…”

Her blushing words make my cock swell even more.

“Whoa, it got bigger…”

“I’m going in, Nao!”

“Un, come on, Onii-chan.”

Her pussy, soaked and slick, takes my cock easily despite it being only her second time.

“Aa♡ Your cock’s going in…♡”

“You’re so cute, Nao…”

“Pamper me more, Onii-chan♪”

“Yeah… I’ll make you love me even more!”

Nuchu♡ — Pachun♡ Pachun♡ Pachun♡ Pachun♡

“Hii♡ So sudden♡”

“How’s that? I know all your sensitive spots!”

I’m the one who developed every inch of her body. I know her weaknesses, and I’m about to target her best spot.

“I’ll tease you to make you even cuter.”

“Fue? W-What… Ohhh~~~♡♡♡”

I rub her clitoris, just above where my cock’s thrusting, with my index finger. That sensitive spot, hit with my special touch, is devastating—

“Ngooo♡ Ohhh… I’m gonna go crazy~~~♡♡♡”

—one strike blows her reason away.

Dochun! — Paan♡ Paan♡ Paan♡ Paan♡

“Hiii♡ No…♡ My pussy and boobs feel so good, I’m numb…!!”

“Feel even better, Nao—you’re mine…!”

“Hahi… Nao’s… Onii-chan’s…♡”

“Good girl! Here, here, here!!”

Paan♡ Paan♡ Paan♡ Paan♡ — Dochun!

*Hahe♡ Ah♡ Ah♡ Ah♡ — Aaaa~~~♡♡♡”

Nao lets out a primal scream, hitting a real climax. Her beautiful face, lost to pleasure, is one she’d never want others to see. But to me, this is her cutest look.

“I’m cumming, Nao…!”

“Ngooo♡ Ha, hahe…♡”

Her pussy, lost in ecstasy beyond understanding my words, makes my cock swell, shooting semen, byukubyuku, into the condom.

(I really want to cum inside her pussy…)

Despite using a beautiful girl’s pussy, I’m frustrated I can’t finish inside.

“Not nearly enough. I’ll keep going until my balls are empty!”

“Ah, auuu…♡”

Drenched in pleasure, Nao faces my unleashed desire as I put on another condom.

…

How much time passed? A dozen condoms ran out, and we’re halfway through the second dozen. My lust doesn’t wane—right after cumming, my cock hardens again.

Paan! Paan! Dochun♡♡♡ — Byurubyururu♡

“Oh♡ Oh♡ Oh♡ Ooo♡ Ah♡… Ahee♡”

Pushi♡ Choro… Jorororo♡

While enjoying Nao’s body, a fluid other than love juices flows from her pussy.

“Nao, you’re peeing?”

“Ah, aaa… Sorry…”

“That’s a lot. Can’t stop?”

“C-Can’t… stop… Sorry, Onii-chan…”

She’s lost control of her lower body, leaking urine.

“It’s okay. I’m not mad.”

“But… you’ll get dirty…”

“Your pee isn’t dirty.”

No brother would get mad over his sister’s pee. I thrust into her pussy, feeling the warmth of her urine.

“Hann♡ It’s… still coming? Hyan♡ Ah♡ Ah♡ Ah♡”

Paan! Zuchu♡ Zuchu♡ Zuchu♡ Jororo… Jororoo… Roro…♡

“Peeing Nao’s so cute… Chu”

*Hahee♡ Chuku, Churu♡ Chuuu… Nn♡”

Kissing while stroking her head.

Dochun♡ Dochun♡ Dochun♡ Dochun♡

“Nnnnn~~~♡♡♡ OHH♡♡♡”

Overwhelmed, Nao climaxes mid-kiss, eyes rolling back.

Her body goes limp.

Pushi! Pushaaaa♡♡♡

Convulsing, she squirts, painting a rainbow in the air.

…

“Nao, you okay?”

“Yup… I’m fine now.”

Despite such intense sex, she recovers in ten minutes.

“I’m tough♪”

“You’re so cute, Nao.”

“Ehehe~♪”

Only Nao can handle such extreme sex. My adorable, sexy sister makes me dote on her even more.

※

“Aya-nee, sorry for stealing Onii-chan…”

“It’s fine, Nao-chan. I’m happy just seeing sensei.”

I haven’t had sex with Ayaka since then—her belly carries a new life.

(Ugh… I wanna have sex with Ayaka too… maybe her ass…)

Present are Ayaka, Nao, and Miyabi, cleaning the bed. All stunning beauties, related to Yukino, and aware of my relationships.

“Yukino-chan didn’t come?”

“Yuki-nee’s doing it with Onii-chan at school.”

“Fufu, every day then?”

“Yup, so unfair.”

True, I’m with Yukino daily, but it’s quickies in the library with Riria or short bathroom breaks. Full-on sessions are limited.

Since we risk getting caught, Riria and Yukino take turns standing guard during bathroom sex.

Speaking of which, recently—

※

Nuchu♡ Nuchu♡ Nuchu♡

“Ann♡ Your big cock…♡ Hitting deep~~~♡”

“Yukino, your voice is too loud…”

“It’s fine… Riria-chan’s watching outside.”

“Right, then… Here! Here!!”

Pachun! Pachun♡ Pachun♡ Pachun♡

“Nhaa♡ Deep in my pussy♡ Grinding so good…♡”

“Go, Yukino! Break’s almost over.”

“Ohh♡ Amazing… I love big cocks♡”

Yukino’s picked up vulgar words from someone. It’s minor compared to past incidents, so I don’t scold her.

Dochun♡ Dochun♡ Dochun♡ Dochun♡ — Dochu!

“Ooo♡ I’m cumming! Cumming~~~♡♡♡”

“Ku… Aa…!”

Her pussy gently tightens, kyuu♡, wrapping me softly. I unleash my pent-up desire into her sweet hole.

Byuru♡ Byururu♡

“Haaan♡ It’s coming…♡”

“Ku… Haa… Feels so good, Yukino…”

(Yukino’s starting to resemble Ayaka… Will she grow into such a beauty?)

As relatives, their bodies might be similar. Still youthful and beautiful, Yukino might become even more stunning. Thinking this, I finish unloading my semen from class.

“Phew… Let’s head back.”

“Yup♪”

We fix our clothes and leave the bathroom.

“Yukino-chi♪ Sounded like you had fun~”

“Riria…”

“Thanks for watching, Riria-chan.”

“Next break’s my turn~”

“Yup, I’ll ring if someone comes.”

“Okay♪”

It’s a routine we’re used to.

…

Next break—

Nuchu♡ Nuchu♡ Nuchu♡

“Nhaan♡ Big cocks are the best♡”

“Don’t teach Yukino those words…”

“But you love being called big cock, right?”

“…Not really. It’s not that big.”

I’m not enough to satisfy Miyabi yet. I need to train more.

“Liar♪ You’re a sex-crazed perv like me.”

“That extreme?”

“Yup. No sex, no life, right… Here♡”

“Ku… So tight…”

Riria can control her pussy’s tightness. When she tenses her abdomen, her walls grip, gyuu♡, squeezing my shaft and glans.

Pachun! Pachun♡ Pachun♡ Pachun♡

“Aaa♡ So good… Best cock ever…♡ Pound me more♡”

“Your pussy’s amazing, Riria!”

Zubo… Dochun♡ Zubo… Dochun♡ Zubo… Dochun♡

“Oh♡ Ngooo♡ That’s… so good♡”

“Go! Here, here, here!!”

I lift her hips with my trained arms, slamming them against my cock, impaling her.

“I’m cumming♡ Cumming like crazy~~~♡ Oooo… OHH♡♡♡”

“Ku… Aaa!!”

I can’t hold back, shooting my load, dobyu♡, deep into Riria, rocking her up and down.

“You’re the best♡ No point getting a new boyfriend…”

“What’s that, a confession?”

“Maybe♪”

Riria laughs lightly.

(We’re weirdly compatible. A different choice, and things might’ve been different.)

I finish unloading into her pussy.

“Phew… Back to class?”

“Yup… That thing earlier? Joking, but serious.”

“Huh?”

For a moment, her face turns serious, then back to her usual playful self.

“Come on, break’s over~”

“Ah, yeah…”

My heart races as we leave the bathroom.

“Sorry for the wait, Yukino…”

“Thanks~♪”

“What were you two talking about?”

“Nfufu, secret♪”

And so, we three hang out happily as always.

※

“Onii-chan!”

“Huh? Oh, Nao.”

“You were spacing out… Tired?”

“Oh, that won’t do, sensei. Let’s lie down.”

Ayaka presses her body against my arm.

“The bed’s ready.”

Miyabi finishes cleaning just then.

“I’ll cuddle too~♪”

“Then I’ll take the other side.”

Sandwiched by two beautiful girls, maybe due to fatigue as Nao said, their warmth lulls me, and my consciousness fades.

…

♪♪♪

“—…Nn? Phone…? Oh, crap!!”

I grab my phone and hit the call button.

“Onii… What’re you doing…? Dinner’s ready.”

“Sorry, I’ll be home soon!”

“…”

“Ai? What’s wrong…?”

“Onii… You’re cheating, aren’t you?”

Her voice is low, confronting my infidelity again.

“Uh, well…”

“It’s fine. I’ve given up on that. Satsuki’s okay with it too. That’s just who you are.”

“…”

“But you’re not serious about them, right?”

“Well, uh…”

“If you plan to ditch Satsuki, I won’t forgive you.”

Her voice carries the most terrifying tone I’ve ever heard.