I'll Be a Younger Sister You Can Be Proud Of
My younger sister came home earlier than usual today. It was because she was in the middle of her school exam period.
"...Oppa, can you grade my test for me instead?"
My sister shouted, thrusting her test paper toward me with a look of intense nervousness.
She was the type to break out in a cold sweat and have her mind go completely blank whenever she was nervous, so she could never bring herself to do something as nerve-wracking as grading her own exams.
I smiled kindly, readily accepted her test paper, and began grading it against the answer key.
While I was grading, my sister stayed locked in her room, trembling with anticipation. Finally, when I finished and called for her, she came out cautiously and asked me.
"S-so, how did it go...?"
I smiled brightly and answered her.
"Congratulations, it's a perfect score! That's my sister for you..."
Only then did my sister's anxious expression melt away, replaced by a radiant smile.
She snatched the graded test paper from me to check for herself that it was truly a perfect score, then beamed even wider and started jumping up and down on the spot.
"Yes! Oppa! I did well, right? I did well, didn't I!"
"Yes, our Hyun-jung is truly amazing. I'm so, so proud of you. You're the best!"
I showered my commendable sister with endless praise. At that, she blushed deeply, looking incredibly happy, and came running toward me with a "thud-thud-thud" before throwing herself into my arms.
She rubbed her face against me for a moment, then looked up with a blissful expression and said,
"Oppa! Give me that as a reward, that thing!"
"Eek... T-that...? That's a bit... Hyun-jung, you're all grown up now..."
"...Tsk... If I tell you to do it, just do it. You talk too much..."
When I showed signs of refusal, my sister muttered in a low, chilling voice with her eyes wide open. I struggled with a troubled expression, but eventually, I gave in.
"Fine, I got it... Just for a little while, okay..."
"Yes! Hehe..."
My sister nodded, smiling as brightly as a giant flower. Then, she hopped onto my lap and curled up on all fours like a cat, crouching down.
In that position, I lightly patted my sister's uniformed bottom with my palm, as if I were giving a cat a "butt-pat," while constantly whispering sweet praises into her ears.
"Our Hyun-jung is the best, the prettiest and cutest in the world..."
"Hehe, it feels so good... Do more, do more~"
...This strange ritual was a kind of "praise ceremony" we had been doing since we were very young.
Perhaps she was a cat in a past life; she loved it whenever I treated her like one and showered her with praise.
It was a bit embarrassing, so we didn't do it often as we got older, but whenever my sister threw a tantrum like today, my heart would soften, and I’d end up doing it against my better judgment.
The big problem with this ritual was that once you started, you had to keep your mouth and hands moving without rest until she was satisfied, which was exhausting.
Today, too, after about fifteen minutes of non-stop effort, my arms grew weak, and it effectively turned from a "butt-pat" into a gentle stroking motion.
As I stroked my sister's bottom, clad in a short school skirt, my hand naturally began to rub over her plain gray Nike panties.
At some point, my sister's breathing began to tremble in a slightly suggestive way.
"......Haa..... Haa..... I-it feels... so good..... Oppaaa...."
"H-Hyun-jung? How much longer do I have to do this...? My knees are starting to hurt..."
"....So what?"
When my sister opened her eyes with a murderous glint and retorted, I hurriedly forced an awkward smile, shook my head, and went back to working my hands diligently.
Even after that, my sister shivered on top of me for a long time, enjoying the sensation, before flipping over to lie on her back in a submissive pose, exposing her belly, and muttering,
"...Okay, pat this side too, quickly."
"O-okay...."
And so, I fell into an infinite hell of praise for another thirty minutes, stroking her lower half.
"Our Hyun-jung is the best, she's amazing..."
"...Ooh.... Oh god..... I-it feels so good.... Just a little more...."
My sister muttered, her face flushed red and her lower abdomen trembling as she kept her knees tightly pressed together, as if trying to endure a ticklish sensation.
By the time the praise ceremony finally ended, my sister stretched out refreshingly, her skin looking plump and vibrant, as if she had sucked the energy right out of me, leaving me a total wreck.
"Yaaawn~ That felt good for the first time in a while! With this, I can do well on tomorrow's exams too. Thanks, Oppa!"
"Y-yeah, that's a relief..."
Exhausted, I forced a smile and waved my hand like a dry piece of straw.
Then, my sister looked at me with eyes full of affection, hugged me tightly with her small chest, and whispered into my ear,
"I'll definitely do well on the remaining exams and become a younger sister you can be proud of!"
Even in that state, I felt a faint smile tug at my lips, touched by her sincerity, and replied,
"Yes, Hyun-jung."
...After that, while walking to Nayeon's house for the group tutoring session, I was lost in deep thought.
The last thing my sister said wouldn't leave my head.
'I'll definitely do well on the remaining exams and become a younger sister you can be proud of!'
...It was a comment that naturally brought a warm smile to my face, but in reality, there was one major problem.
The fact was that the human being known as her "Oppa" was earning money in a very shameful, far-from-proud way.
...Judging by the circumstances, it seemed that even Nayeon's mother didn't truly believe her daughter's grades would improve.
In all likelihood, the daughter was just an excuse; the real goal was to threaten the tutor coming to the house to easily satisfy her own sexual desires.
'...That means I wasn't hired as a tutor, but basically as a male prostitute... Ugh....'
...It's not like I have a sense of duty toward the job of being a tutor.
I don't feel a sense of responsibility toward Nayeon, Ye-eun, or Seung-hee, whom I haven't known for very long.
This was purely my own stubbornness, a meaningless struggle to become an Oppa my precious younger sister could be proud of.
I clenched my fists, looked up at the sky, and made a silent vow.
'...Yeah, even if it’s just out of spite, I will definitely raise these girls' grades... Because I am their tutor...!'
With that resolution, I made my way to Nayeon's house.
However, as soon as I entered the foyer, the sound of three female students laughing boisterously reached my ears, and the resolve I had just hardened felt like a sandcastle crumbling to pieces.
Feeling completely intimidated, I cautiously opened the door to the room and greeted them.
"A-ah, hello, everyone..."
"Ahahaha! I'm telling you, it's crazy, crazy..."
Ye-eun was laughing and chatting behind Nayeon's back, carefully curling her bangs with a hair iron while looking in the mirror.
Nayeon was sitting with her knees pulled up, hugging them with her arms, giggling with her signature delinquent look in her eyes. Seung-hee was leaning comfortably against Nayeon, playing on her phone.
Of course, this cozy scene, which looked like girls playing innocently, changed in an instant the moment I opened the door and entered.
Nayeon was the first to grin, waving her hand in greeting as she shouted,
"Teacher~ Why are you so late? Hehe."
With that, Nayeon tapped the seat next to her, as if telling me to sit there. Through the gap in her legs as she sat with her knees up, I could see her panties peeking out.
I hesitated, then reluctantly and timidly sat down next to Nayeon.
And, about 30 minutes after that.
"Uuugh.... Ugh... Hmph...."
"...Alright, from now on, we're going to have a contest to see how many times we can make the teacher's cock twitch just by the smell! Shall I start first?"
Ye-eun grinned, pinning my arms and legs so I couldn't move, then rolled up her short-sleeved school shirt to her shoulders and pressed her bare arm