When I was dating my wife, my younger sister-in-law was already a sophomore in college.
Because she had been attached to her older sister since childhood, she often ended up caught in the middle as a light bulb, and I didn’t even dare move my hands randomly, afraid she would see me being intimate with my wife and go spread it around.
Time passed quickly. Several years later, I finally married a wife, moved into my own new house, and enjoyed the blissful world of two. And my sister-in-law had long since grown from a naive college student into a mature young woman.
The sisters' bond remained strong; she would often come to my house to play with her sister. After the honeymoon phase, during idle moments, I would also observe her increasingly voluptuous body. She wasn't tall, less than 160 cm, petite and cute, but her breasts were well-developed. Through intentional or unintentional physical contact, I had long been aware of this.
Soon, my wife became pregnant. We both liked children very much, so we agreed to do that less often. But the fire in my heart was hard to calm, and my gaze unconsciously fell on my sister-in-law.
Actually, I can feel that she isn’t completely without feelings for me either. She would secretly glance at me with her eyes, lightly brush against me when walking, and when we went for walks together she would unconsciously hook her arm through mine. Before, I thought of her as my wife’s younger sister and didn’t think deeply about it. Now it’s different. I haven’t touched my wife for several months, and my desire has been piling up badly. There’s only one thought in my mind—possess her.
That day, my wife went to the hospital for a prenatal checkup, and I was doing housework at home. The doorbell rang. Opening the door, it was my sister-in-law. She had brought a few CDs my wife liked from home, saying they were for prenatal education for the future baby.
I took the plate and placed it next to the TV, invited her to sit, and went to the kitchen to make coffee. Then I found there was no coffee left—she really likes it, I always make her some when she comes over. I had to let her watch the DVD first while I went downstairs to buy some.
Only when I reached downstairs did I remember: next to the DVD player were mixed two adult films and one Category III film. I inwardly cried out in alarm—if she saw them, her opinion of me, her brother-in-law, would be ruined. I hurried back.
When I got home and opened the door, it was already too late.
My sister-in-law was sitting on the sofa, a plot-driven Japanese AV playing on the TV. The man and woman in the film were still in the flirting stage. I quickly grabbed the remote to change the disc, but she flatly refused, blushing and saying, 'I'm not a child anymore, watching can teach me a thing or two.'
Helpless, I had to brace myself and sit down to watch with her.
On the screen, the man and woman quickly undressed and entered the deep stage. The man teased the woman's ears, neck, and breasts with his tongue, then moved down to attack. The woman kept moaning with pleasure. I stole a glance at my sister-in-law; her face was already flushed red, her legs were clamped tighter and tighter, and her body was unconsciously writhing.
I quietly moved closer to her.
At that moment, the phone rang. It was my wife calling, saying she had run into a female classmate and wouldn't be home for dinner.
Now I'm completely at ease.
After hanging up the phone, I hesitated no longer and reached out to pull her into my arms. She struggled in the throes of desire for a moment before finally softening. I lowered my head to kiss her, and she instinctively clenched her teeth. I slipped my hand into her top, found her nipple through her bra, and gently pinched it. She let out a soft 'oh,' and I took the opportunity to slip my tongue inside.
The natural scent of a virgin kept stimulating me. While kissing her, I unfastened her bra from behind. Her B-cup breasts were fully exposed. I rubbed her nipples with my fingers, then turned to kiss her earlobe. Soon, she was completely consumed by lust and lost all resistance.
I pushed her top up, lowered my head, and gently sucked her nipple. The early summer weather wasn't hot, but she had a fine layer of sweat, her breasts carrying a faint salty taste. I was already painfully hard; I took off my pants and guided her small hand to grasp me.
It was her first time touching a man's thing, she was so nervous she didn't know what to do, blushing as she said: "Brother-in-law... this thing is so big... mine is so small... no more... I'm scared..."
I didn't give her a chance to refuse, lifted her skirt, pulled down her white panties, and lowered my head to kiss that spot. Her nearly hairless pussy had only sparse pubic hair, full and tight, no odor, only a fresh body scent. I licked and teased relentlessly; she soon moaned continuously, and pleas for mercy came one after another.
I was already overflowing down below. I pressed the tip of my shaft to her entrance and gently rubbed her clit. She had never experienced such stimulation, and soon reached her first climax, with her love juices surging out in torrents.
I aimed at the entrance and forcefully sank my body down.
A virgin really is different. The tight flesh of her passage wrapped around me firmly; even just the glans entering made it difficult to go any further. I didn’t dare act rashly, leaned down and took her nipple into my mouth again, sucking while gently moving my lower body. After she adapted, I held her waist and began shallow thrusts. When I advanced to one-third, I met resistance—that was the proof of her virginity.
I took a deep breath, gripped her slender waist, and thrust in hard.
Immense pleasure and the pain of losing her virginity struck simultaneously. She opened her mouth to cry out, but I immediately kissed her, turning the cry into a muffled groan. I closed my eyes, enjoying the feeling of that tight, sucking embrace; her vagina continuously contracted, sucking like a little mouth.
Under continuous caressing, the pain gradually faded away, replaced by waves of soreness and itchiness. She looked at me shyly, clamping her legs around my waist, and her lower body began to wriggle. I deliberately didn’t move and asked softly, “What’s wrong?”
"Brother-in-law... something feels weird down there... it hurt a lot just now, but it doesn’t hurt much now. It’s a little numb, a little itchy..."
“So your brother-in-law isn’t moving anymore?”
She grew anxious: "Can you just move a little... you're so big, stretching me so full..."
I began thrusting with nine shallow strokes followed by one deep one. For her, who had just lost her virginity, this rhythm was most suitable. Soon she was panting娇喘连连, moaning失神地: 'Mmm... brother-in-law... I love you... I'll be with you forever...'
To completely possess her body and soul, I deliberately pulled back and stopped at the entrance of the hole. She had developed a taste for it and kept writhing her butt upward to meet me. I teasedly asked: “What do you want to do?”
"You... come in..."
I vigorously kneaded her breasts, my lower body thrusting all the way in. The sensation of the glans scraping past her cervix was intense. She completely surrendered, wrapped her arms around my neck, and whispered in my ear, 'Brother-in-law, from now on you are my husband... I will love you forever.'
I stopped holding back, thrusting hard while training her. Made her say 'fuck my cunt', say 'master', admit she was a sex slave. She was shy at first, but later fully cooperated, softly moaning: 'Master... this little slut's pussy is so itchy... please use your big cock to help your slave...'
I thrust vigorously over a hundred times, releasing in a torrent as we climaxed simultaneously, shooting all the semen accumulated over three months into her tight, hot body.
After a few minutes, as I was about to get up, she wrapped her legs around my waist and whispered, 'Master... your servant feels so good... I want to be connected to you forever...'
After hearing this, my desire rose again. With the lubrication from before, I began another round of thrusting and training.
From that day on, my younger sister-in-law became my secret sexual partner.
When my wife was at home, we pretended to be ordinary sisters and brother-in-law; when my wife wasn't there, she would take the initiative to send messages or come directly to my door. Each time was more uninhibited than the last. She learned various positions, learned to moan wantonly beneath me, and also learned to clamp her legs tight after climax, not letting me withdraw immediately.
On the surface, she still came to see her sister, deliver things, and help with housework, but as soon as her sister-in-law wasn't around, her gaze would change. Sometimes she would deliberately wear something shorter and tighter, swaying her hips slightly when walking; sometimes she would find an excuse to walk behind me, her breasts brushing against me subtly.
At first, I pretended not to know, but later I simply stopped hiding it.
Once my wife went to the maternity center for a prenatal class and wouldn't return until afternoon. My sister-in-law came at noon. As soon as the door closed, she pressed me against the entryway and kissed me. The kiss was urgent, her hand already in my pants. I carried her to the sofa, lifted her skirt, and found she wasn't wearing underwear underneath.
"Did you do this on purpose today?" I asked.
She nodded, blushing, and spread her legs herself: "Missed you... missed you these past few days."
I lowered my head and kissed her, using my tongue to make her wet, then entered fully. She was much more relaxed than the first time, still tight and hot inside, but she actively lifted her hips to meet me. I thrust deep and hard, she bit the back of her hand to suppress her cries, afraid the neighbors would hear. When she climaxed, her whole body tensed, her inner walls contracting in waves, squeezing me until I came too.
Afterward she lay on my chest, her voice still a little breathless: “Brother-in-law... when your wife isn’t around in the future, can you call me over more often?”
I pinched her nipple: "Take the initiative yourself."
She let out a "mm" and buried her face even lower.
Then she really became active.
Sometimes she'd send a message in the afternoon: 'Sister went to the hospital, I'm coming over.'
Sometimes after my wife falls asleep at night, she would quietly sneak over from the guest bedroom and slip into my blanket. We tried our best not to make a sound, but once we truly entered, suppressed gasps would still spill out. She learned to call me 'Master' in a breathy voice under me, learned to clamp her legs tight after being creampied, learned to use her mouth to get me hard again.
My wife's belly grew bigger and bigger, and her mobility became increasingly inconvenient. Our sex life almost completely stopped. All the suppressed desires were poured onto my sister-in-law. She came over more and more frequently—sometimes three times a week, sometimes two days in a row. Every time before leaving, she would carefully cover up any marks on her body, change into ordinary clothes, and revert to being the well-behaved younger sister who was just visiting her sister.
But once the door closed, she became another person again.
One night when she came, she carried a slight smell of alcohol.
"Class reunion, had a couple of drinks," she explained, then knelt down directly and took me into her mouth. Her technique was much better than at first, her tongue circling the tip nimbly, occasionally deep-throating. I pressed the back of her head, making her take me deeper. She didn't resist; instead, she made satisfied moans. Just as I was about to finish, she pulled back and looked up at me:
“Inside.”
I pulled her up and pinned her against the wall to enter. This time was especially fierce. Her legs wrapped around my waist, and each time she was thrust to the deepest point, she let out short cries. When her climax came, her whole body tensed, her insides gripping me tightly. I bit her shoulder and ejaculated everything inside.
Afterward, she leaned against me, her breathing still not steady.
“Is this really okay?” she suddenly asked.
I am silent for a while.
"Do you want to stop?"
She shook her head, burying her face in the crook of my neck: "I don't want to. It's just... occasionally I get scared."
I held her tighter.
Outside the door are the lives we each must maintain—she has her studies, her parents; I have a wife, a child about to be born. But inside the door is a different set of rules, where we can do as we please, scream as we please, and release the desires pent up during the day over and over again until they are completely spent.
And we all know that as long as we want to continue, no one will say it's over first.
In the month before my wife was due to give birth, my sister-in-law came over almost every other day.
Sometimes it's during the day, curtains tightly drawn, sunlight only leaking through the gaps; sometimes it's late at night, not stopping until her legs are weak. She starts actively requesting more positions—being entered from behind, being pressed against the floor-to-ceiling window, having her wrists tied. I satisfy her every time. After each internal ejaculation, she keeps her legs tightly closed for a long time, as if trying to keep everything inside.
The day the child was born, the younger sister-in-law was also at the hospital.
She held her sister's hand, her eyes rimmed red. I stood to the side, watching the sisters leaning on each other, but in my heart flashed those secret images—the way she moaned beneath me, her dazed expression after being creampied, the way she actively knelt down to take me in her mouth.
Once desire is ignited, it is difficult to extinguish.
And that door had long since been flung wide open.
It can no longer be shut.
After the child was born, the house became completely chaotic.
My wife is in her postpartum confinement period. During the day, a confinement nanny takes care of her, but at night, she often needs someone to soothe the baby. In name, I'm a responsible husband and father, but in reality, I spend more energy figuring out how to see my sister-in-law.
She was more careful than before.
When coming over, she would send a message in advance to confirm that my wife was asleep and the postpartum caregiver wasn't in the living room. Sometimes she only stayed for half an hour, sometimes she could steal one or two hours. Every time we met, she seemed as if she had been starving for a long time, pouncing on me to kiss me as soon as she entered the door, her hands urgently unbuttoning my pants.
“These past few days… I’ve missed you to death.” She buried her face in the crook of my neck, her voice trembling.
I pinned her against the wall and entered from behind. She bit the back of her hand, trying not to make a sound. Inside, it was wetter and hotter than before, each thrust producing subtle wet sounds. I reached around to rub her clitoris, and she quickly tensed up, her inner walls contracting violently. I didn't stop, continuing to thrust to the deepest point until I also came inside.
Afterward she clenched her legs tightly, not letting the semen flow out, and leaned against me, panting.
"Next time... can it be longer?" she asked softly.
I pinched her nipple: "Depends on the opportunity."
Opportunities always exist.
During her postpartum confinement, my wife had limited mobility and often slept for long periods in the afternoon. My sister-in-law would use the excuse of 'visiting her sister and nephew' to come over, but in reality, she spent most of her time entangled with me in the guest room or master bedroom. Once, we were in the middle of it when the confinement nanny called from outside the door. She froze in fear, but her inner walls clenched even tighter. I covered her mouth and slowly continued thrusting until she climaxed again in extreme tension.
That kind of stimulation became addictive for her.
Then she began to actively ask for more stimulating scenarios—in the living room sofa, on the kitchen counter, and once even on the balcony (with the curtains drawn tightly shut). After each internal ejaculation, she would keep her legs clamped shut for a long time, as if trying to lock everything inside her body.
On the day the child turned one month old, many relatives came to the house. My sister-in-law was also there. She held the child, smiling very gently, sitting and chatting side by side with her sister. I stood nearby socializing, but my peripheral vision kept drifting towards her. She would occasionally look up at me, a flicker of meaning in her eyes that only I understood.
After seeing off the guests in the evening, my wife was exhausted and went to bed early. My sister-in-law proactively stayed behind to 'help.'
As soon as the door closed, she pulled me into the guest bedroom.
This time she was exceptionally proactive. She took off her clothes herself, straddled me, and guided me as she slowly lowered herself. When she reached the deepest point, she let out a soft gasp, then began to move on her own. I held her waist, watching her intoxicated expression, occasionally reaching out to caress her breasts. Her movements grew faster and faster, and she soon climaxed, her inner walls tightly gripping me.
I flipped over and pinned her beneath me, continuing to thrust. Her legs wrapped tightly around me, actively meeting my movements, her voice suppressed yet wanton: 'Master... deeper... shoot inside...'
I satisfied her. After ejaculating everything inside, she clamped her legs tightly shut, looking at me with dazed eyes.
“I think... I’m kind of falling in love with this feeling.” She said softly.
I don't answer, just pull her into my arms.
Days passed like this, one by one.
As the child gradually grew older, my wife recovered almost fully, and our sex life slowly resumed. But the things between me and my sister-in-law didn't decrease at all. She learned to talk to me nonchalantly during family gatherings, learned to act obediently in front of her sister, and also learned to completely let go when it was just the two of us.
Once she stayed overnight at my place.
At night the child cried and made a fuss, and his wife went to soothe him. She quietly slipped into the master bedroom and lay down beside me. We tried our best not to make any sound, but when I entered her, she still let out tiny, broken whimpers. I covered her mouth with my hand and thrust deeper little by little. She climaxed under extreme restraint, her body shaking violently, the inner walls contracting again and again.
Afterward she whispered in my ear: “Next time... I want to be tied up.”
I agreed.
Once desire is ignited, it is difficult to extinguish.
And that door had long since been flung wide open.
It can no longer be shut.
The story continues.
Every time she pushed open the front door, every time we locked the bedroom door, it felt like confirming the same thing—
Some boundaries, once crossed, can never be returned to.
Every time she pushed open the front door, every time we locked the bedroom door, it felt like confirming the same thing—some boundaries, once crossed, can never be returned from.
When the child was six months old, the family finally relaxed a little. The wife started taking the child out to sunbathe and participate in mom group activities, often not at home during the day. The younger sister-in-law seized these gaps and came more frequently.
Sometimes in the morning, she uses the excuse of delivering something; sometimes in the afternoon, she directly sends a message: 'Are you free now?'
If I reply 'The door isn't locked,' she will appear within twenty minutes.
As soon as she came in, she was often already wet. Once she was wearing a skirt with nothing underneath, and she directly pinned me onto the sofa and climbed on top herself. When I went in to the deepest point, she let out a satisfied sigh, then started rocking herself. I held her waist and watched her intoxicated expression, occasionally reaching out to rub her breasts or clitoris. She climaxed quickly, and her inner walls clenched so tightly that I almost immediately wanted to cum too.
I held back, flipped her over, and entered from behind. She buried her face in a pillow, trying to keep her voice as low as possible, but each time I thrust deepest, a sob would escape. I reached around to the front and quickly rubbed; she soon climaxed again, her body shaking violently. Only then did I speed up and ejaculate everything inside.
Afterward, she lay motionless, semen slowly trickling down her thigh. I helped wipe her clean, but she suddenly grabbed my hand and placed it back between her legs:
“Once more... I want it.”
I got hard again. This time, I had her lie on her back, her legs over my shoulders, entering her deeply and slowly. She looked into my eyes and voluntarily said things she usually wouldn't dare, calling me 'Master,' saying she was 'only brother-in-law's sex slave.' Those words excited me more than ever before, and I came more and deeper than any other time.
She kept her legs clamped together for a long time before finally letting go.
“I think I really can’t do without it anymore.” She said softly.
I didn't respond, just kissed her forehead.
Days slipped by like this.
On the surface, we were still just ordinary brother-in-law and sister-in-law. At family gatherings, she would help her sister with the children, talk to me normally, and occasionally even deliberately joke in front of others, saying 'Brother-in-law is so good to sister.' No one noticed anything unusual.
But only we know what the scene is like behind the door that’s been locked from the inside.
Once she came to stay for the weekend.
At night the child was asleep, and his wife was asleep too. She slipped into my room and crawled under the covers. We had almost no foreplay; she was already soaked, and I entered her directly. She buried her face in my chest, suppressing every sound, relying only on her body’s reactions to tell me how comfortable she was. At the peak, her whole body tensed, her nails dug into my back. After I came inside her, she still clenched her legs and said softly:
“Don’t come out... stay a little longer.”
I obeyed her.
After a long time, she finally let go and got up to return to the guest bedroom. Before leaving, she glanced back at me with a complicated look in her eyes:
"If one day... sister finds out?"
I fall silent.
She shook her head herself and smiled: 'Forget it. Don't think about these things.'
The door was gently closed.
Lying in the dark, listening to her footsteps fade away, I knew clearly—this door had opened too completely, and could never truly be closed again.
It took a long time before she let go, stood up, and prepared to return to the guest bedroom. Before leaving, she turned back to look at me, her gaze complex:
"If one day... sister finds out?"
I fall silent.
She shook her head herself and smiled: 'Forget it. Don't think about these things.'
The door was gently closed.
Lying in the dark, listening to her footsteps fade away, I knew clearly—this door had opened too completely, and could never truly be closed again.
Desire is still burning.
And the story is still continuing.
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