(Erotica) The Runaway Sister-in-Law and the Secret Compatibility Test - Short Story

When I came home, my sister-in-law was there.

"Hey... sister-in-law... what brings you here at this hour?"

Kyungtaek and his sister-in-law were the same age, so they spoke casually and comfortably. His outspoken sister-in-law grumbled at him with a clearly irritated voice.

"What do you think? I'm so furious with my brilliant husband that I had to get out. Sorry, but let me stay here just for today..."

"We don't mind, but... what did hyeongnim do this time to piss you off?"

Kyungtaek asked his wife why his sister-in-law seemed so upset as he went to change clothes.

"Looks like hyeongnim was being stingy again. Got mad about her buying clothes... she said it was the first time in five years she bought something for herself, so she has a right to be angry..."

"Tsk tsk... how can a man be so cheap..."

Kyungtaek shook his head, recalling his brother-in-law's rigid personality.

Anyone would think he was a morally upright teacher—he was that conservative and tight-fisted.

In contrast, his sister-in-law had a bold, open personality, running a clothing stall at the market.

It was almost admirable that these two with such opposite personalities had stayed married for nearly ten years without divorcing.

Actually, the same could be said about Kyungtaek's own household.

Kyungtaek was lively and passionate, while his wife was extremely introverted to the point of being excessive.

Before marriage, her delicate, shy appearance had seemed charming, but after marriage, seeing that same demure look every day had become boring.

He'd repeatedly encouraged—half urging, half threatening—her to become more assertive, but it seemed her nature just wouldn't change.

So his mother-in-law would sometimes joke that the two couples should swap partners—it would be a perfect match.

Anyway... to cheer up his long-absent sister-in-law, Kyungtaek, his sister-in-law, and his wife went out for dinner and then to a karaoke room.

Kyungtaek, known as a singer at his company, was used to karaoke, but his sister-in-law and wife seemed out of practice and were busy flipping through song books.

"Hey... don't look from behind... look from the front... how would middle-aged women know songs from the back?"

"Here we go again with someone disrespecting the aunties... we know the latest hits too, you know..."

His sister-in-law casually brushed off Kyungtaek's comment, picked a song, and started singing.

Wax's "Auntie" blasted out in a fast rhythm, and his sister-in-law began singing, twisting and swaying her body.

She must have been taking dance lessons recently—her hips and waist moved with unusual skill.

She placed a hand on her waist, and during the chorus, she shook her hips and even her breasts, singing passionately.

"You come out and dance with me too!!"

Kyungtaek whispered to his wife's ear. But his introverted wife just smiled and shook her head, shaking a tambourine.

'Ugh... this bear...'

Kyungtaek felt sorry for his wife, who couldn't really enjoy herself even when brought out like this, and moved toward his sister-in-law to join her dancing.

His sister-in-law, perhaps bored dancing alone, grabbed Kyungtaek's shoulder and began swaying her body even more sensually.

Kyungtaek swayed with her, and gradually, their bodies drew closer, shaking together like they were dancing salsa.

In the tight space, his sister-in-law's breasts repeatedly brushed against Kyungtaek's arm.

She didn't care at all—instead, she pressed her body even tighter against him as they danced.

The karaoke session continued to lift his sister-in-law's mood, and Kyungtaek passed around beer cans to add to the fun.

Then, his wife got up to go to the bathroom, and Kyungtaek's requested song started playing.

Shin Seung-hoon's "Love That Can't Be Seen"—a song Kyungtaek loved singing in school. He stepped forward, struck a pose, and began singing.

"Mom... this is my favorite song... My brother-in-law really knows music..."

His sister-in-law, already having drunk two cans of beer, clapped and stepped forward.

"Whenever this song came on back in my day, men would flood me with blues requests... Today, how about I dance with my son-in-law?"

She slurred slightly as she wrapped both arms around Kyungtaek's neck and leaned her body against his chest.

Kyungtaek lightly placed one hand on her back, swaying to the beat of the music.

As the song reached its climax, his sister-in-law's arms tightened around his neck, pulling her body even closer to his.

She pressed her entire body against Kyungtaek, swaying to the rhythm, slowly rubbing herself against him.

At first, he took it as just the mood, but his sister-in-law's sensual movements began to excite him.

Looking into her eyes, she seemed to be asking for a kiss, her eyes half-closed, lips slightly parted.

But his wife could walk in at any moment—how could he kiss her?

Instead, Kyungtaek gently ran his hand over her back, then slowly moved it down to lightly touch her buttocks.

But she didn't pull away—in fact, she pushed her hips back toward his hand.

Kyungtaek placed his hand on her buttocks again and began gently stroking up and down.

He could feel the seam of the panties beneath her jeans through his palm. He moved his fingers along that line.

His voice was off-key and the rhythm all wrong, but neither noticed—Kyungtaek and his sister-in-law were completely absorbed in dancing.

She was probably drunk, but she pressed her body tightly against him, swaying sensually—too much, almost.

His cock, already hard since earlier, now poked against the zipper of her pants.

She briefly opened her half-closed eyes at the sensation, but didn't pull away. Instead, she swiveled her hips side to side, stimulating his cock.

'Damn... why is sister-in-law acting like this today? Is she trying to make me suffer?'

Kyungtaek thought to himself, imagining his sister-in-law's pussy hidden beneath her clothes. Just the thought made his cock throb harder.

"Hey... today you're totally cheating on my husband with him... isn't this a bit too wild?"

His wife had quietly come back in, watching her husband and sister dancing the blues, and said it with a smile.

Kyungtaek flinched and quickly removed his hands from his sister-in-law, but she kept holding him and said to her sister.

"Hey... since I'm your husband, I might as well dance like this... are you jealous of me now?"

"Fine. I'll lend you my husband today, so go ahead and release all the stress from dealing with hyeongnim..."

His kind, gentle wife said it—whether as a joke or seriously, no one could tell.

"Hey... am I some object you can lend out?"

Kyungtaek grumbled, embarrassed to keep holding his sister-in-law in front of his wife, and sat back down.

His sister-in-law followed, gulping down beer, gazing at Kyungtaek with a strangely suggestive look.

After an hour at the karaoke room, the group returned home and dispersed to their rooms.

Kyungtaek, still aroused by his sister-in-law, caressed his wife's delicate breasts and whispered seductively.

"Honey... shall we burn up tonight? Huh?"

"I'm on my period right now... you know that... let's just sleep"

"Ah... right..." Kyungtaek felt both embarrassed and annoyed, and lay back down.

His wife, apparently exhausted, soon began lightly snoring.

Kyungtaek tried to sleep, but his sister-in-law's actions at karaoke and

the suggestive glances she gave him while drinking beer kept circling in his head.

And even now, he could still feel the sensation of her against his cock.

Kyungtaek had no choice but to get up.

With this feeling... I'll need at least half a bottle of soju before I can sleep... Kyungtaek went to the kitchen and started gathering soju and snacks.

"Hey... sneaking a drink all by yourself? That's kind of mean"

His sister-in-law walked into the kitchen. She wore his wife's shorts and a cotton T-shirt. She must have taken a shower—her hair was still damp.

"Uh... couldn't sleep, so I thought I'd have one more drink before bed... want to join me, sister-in-law?"

"Sure... I was just getting thirsty anyway... I need to wet my throat... but if we drink here, your wife might wake up. Let's go to my room."

So Kyungtaek carried a tray, and his sister-in-law brought the soju bottle and glasses to the room.

In the middle of the room, her jeans from earlier lay inside-out on the floor.

The memory of his cock touching those jeans returned, and his cock began to stir.

Kyungtaek poured a shot of soju for his sister-in-law and filled his own glass.

"Drink up—forget all your troubles tonight. Life's full of ups and downs"

His sister-in-law tilted her head back and downed the soju in one go, then handed her glass back to him.

"That's right... that's right... why keep thinking about it..."

Kyungtaek and his sister-in-law quickly exchanged shots. Her face gradually flushed as she said to him.

"You know... I really like straightforward men like you, my son-in-law... I don't even know how I ended up with that miserly husband... don't you agree?"

"Yeah... like what my mother-in-law said, you and I would be a perfect match personality-wise... haha"

"Only personality-wise? Our secret compatibility might be good too..."

His sister-in-law, getting tipsy, started talking suggestively without hesitation.

She'd never been the type to speak politely, working in the market all day... but anyway, she was acting unlike her usual self tonight.

"Secret compatibility... haha... since we're on the topic, should we test it?"

Kyungtaek lightly teased, tossing out a joke.

"Back at karaoke, I could tell you're well-endowed, son-in-law..."

"Whoa... sister-in-law noticed that... that's supposed to be top secret..."

His sister-in-law glanced suggestively at his crotch. Kyungtaek took her hand and moved closer.

"How about we check our compatibility, sister-in-law?"

Then he guided her hand into the pajama pants at his crotch.

She fumbled inside, reached his cock, and began slowly stroking it up and down.

His cock, sensing her touch, slowly lifted its head and stiffened.

"Son-in-law... still in your prime... so sensitive... my husband, the moment I touch him, he pulls his head in like a turtle..."

She pulled her hand out, gazing enviously at Kyungtaek's pajamas, where his cock stood like a tent.

Kyungtaek moved beside her and gently wrapped an arm around her shoulder.

Whether from alcohol or excitement, her body was quite warm.

Now Kyungtaek's hand began gently stroking the front of her shorts.

She twisted her body slightly and leaned into him.

Kyungtaek raised his fingers and began stimulating her pussy mound through the fabric.

"Aaah... ah... son-in-law... ah... why are you doing this... aang... aaang..."

She moaned, twisting her body and pressing even closer into Kyungtaek's chest.

The thin fabric of her shorts was now damp in the front, as if she'd leaked a little pee.

She could bear it no longer and lay down on the spot.

"Aaah... son-in-law... I'm so drunk now I won't remember anything... do whatever you want... aah~~"

"I like women who black out like this... heh heh..."

Kyungtaek lifted her top and began feeling the curves of her breasts with his hands.

Not as perfectly shaped as his wife's, but twice as large.

Kyungtaek gripped her breast in his hand and began licking and sucking the nipple that protruded forward.

His tongue moved rapidly over her nipple, fluttering like a moth's wings.

"Nael. nael. nael. nael... heup heup... nael. nael. nael. nael..."

"Mom... oh god... oh god... aahh... aahh..."

Overwhelmed by the concentrated stimulation on her nipples, she could only cling tightly to Kyungtaek's waist.

Kyungtaek sucked her wet nipple and gently bit it.

She winced in pain and clutched his waist even tighter.

"Wanna bite mine too?"

Kyungtaek asked, gently stroking her pained breast, and she nodded.

Kyungtaek took off his pajamas and lay down. His sister-in-law opened her round mouth and carefully took his erect cock into it.

Kyungtaek pulled her body closer and slid his hand into her shorts, stroking her panties.

She slowly licked his cock with her tongue. Somehow, the licking excited him more than actual sucking.

Feeling good, Kyungtaek grabbed her hair and said.

"Now... I'm not your son-in-law anymore—I'm your lover. Suck until I cum."

"Then what about my hot pussy?"

"Don't worry... I can go five times a night, usually... heh heh"

When he let go of her hair, she lowered her head again and sucked his cock hard, pulling the skin back like it might tear off.

His cock was so engorged with blood it felt like it might burst at the glans.

Then she licked again... alternating strong, soft, strong, soft, medium, soft—her tongue continued its work.

Kyungtaek, excited by a level of service he'd never received from his wife, sweated profusely.

The more excited he became, the faster his fingers moved inside her panties.

"Uheu uheu... god... uheuheu, it's gonna be pulled out by the roots... uheu... uheu"

"Heeuup~~ heupheup... tssseuup, tssstssseuup"

"Ah... it's coming... I'm cumming... hmm."

Suddenly, cum gushed from Kyungtaek's cock, and foam from the cum scattered around his sister-in-law's mouth.

She stuck out her tongue and scooped the cum foam into her mouth.

"Now... Kyungtaek, you have to make me happy too, right?"

She approached Kyungtaek, still dazed from excitement, took off her shorts and panties, spread her legs, and lay down.

Between her white thighs, thick pussy hair looked delicious.

Kyungtaek crawled toward her pussy like a dog and said.

"Today, two people with perfect chemistry are going to fully match their compatibility... wait for it... I'll make you drip nonstop... heh heh"

That night, the room echoed with the sound of his sister-in-law and son-in-law pounding the mortar together, their compatibility test continuing all night long.