It started completely by accident.

I was walking from the garage through the kitchen and on my way to the bathroom and as I passed by my older sister Abby who happened to be bent over moving her clothes from the washer and into the dryer, for no reason at all and with no premeditation, I smacked her big ass. However, my hand didn't land on either cheek; it landed almost perfectly in the middle.

Abby emitted an 'Ooof' and as she was straightening up quickly, she bumped the back of her head on the upper rim of the dryer's door. She yelped with pain and it seemed to have stopped her from chasing after me.

I was cautious coming back from the bathroom to resume working on my bike in the garage. But, when I passed her again, she turned around quickly but didn't say anything. She only gave me a hurt look. I didn't give it much thought at the time and chalked my luck to the pain in her head which stopped her from retaliating.

That night, I couldn't help replay things in my head and more details became crisp in my head. My sister was wearing very soft, thin cotton sweats. I could clearly remember the soft feeling under my fingers. She might not have been wearing underwear even. Then, her 'Ooof' didn't sound like pain at all, only the 'Oww' after her head bump expressed pain.

Anyway, it didn't matter. By morning, I had almost forgotten about the incident. Abby never mentioned anything or changed her attitude towards me.

The next time something else happened was a couple of weeks later. Again, Abby was doing her laundry, but this time it was intentional on my part. I waited until she started loading the dryer, I pretended to be going for something in the fridge and smacked her again on her soft rump. This time however, my aim was intentional and I went for the area between her cheeks and right on where her pussy would be. It wasn't a hard smack. My intention wasn't to hurt her, only startle her. I don't know whether she was expecting it or not, but she didn't react as I expected. A soft, surprised 'Oooh' escaped her lips, but she didn't try to straighten up; probably she was afraid of hitting her head again.

This time I paid closer attention. She was wearing what appeared to be baggy boxer shorts; and I felt the same thing under my finger: squishy softness. But, what really intrigued me the most was her lack of negative response.

See, Abby is seventeen and being two years older than me gave her a certain authority over me that she never failed to exercise until now. Usually, she would yell or scream whenever she was upset, and call me names if I were the cause and generally boss me around. Although I didn't put up much with it since I surpassed her in height, she still did it from time to time. It was odd for her to take abuse from me without reciprocating or at least some vocal disapproval. And again, her behaviour and attitude towards me never changed.

We would have the same talks, the same quarrels, the same meals with nothing out of the ordinary in her behaviour. She never mentioned it, never complained and never berated me. It's as if I didn't do a thing to her.

From that second instance on, I kept an eye out for potential opportunities to see how far I can push her and her remaining the same way.

A month or so later, coming back from my girlfriend's, I again found Abby doing her laundry but this time, she was in a tartan miniskirt.

As she bent over in front of the washing machine—we had a front-loading one—her skirt came up just to the bottom of her full ass, just short of showing her underwear. I stood in the doorway watching her. She went through her motions without giving hints of her noticing me behind her. I definitely enjoyed the show.

To this day, Abby has the same nicely rounded full ass. Not too big, but definitely not small or flat. I would say just right, the kind that you can't help but notice; a clearly defined upside-down heart.

I walked over to her, but this time, there was no smacking. I quickly reached between her thighs and quickly swiped my hand upwards the length of her crotch in a rough attempt at caressing her pussy over her panties. However, I was the one to get surprised as there were no panties and my hand landed directly on her hairy pussy and as I swiped up, my fingers passed over her flesh and I could clearly feel my middle finger passing between two warm, silky lips!

"Ooooh!" came her surprised reaction.

However, she didn't move and didn't yell at me. Despite her inaction, my mind carried the original plan and started to leave quickly before my mind registered that she's not objecting or trying to stop me.

As I walked away, slowly, my mind started going over the details of what just happened and I was amazed at the fact that I seem to have gotten away with rubbing my hand on my sister's bare pussy!

Why wasn't Abby upset? Didn't it bother her that I just did that without her permission? I just molested her and she should be furious with me. Again, no reaction later, no reprisal, no mention and no change of behaviour. I was truly puzzled. Was I imagining things? Did I dream of doing those thing and in reality didn't? To my mind, it didn't make sense. How can she ignore those things completely?

I tried researching that kind of behaviour online but came up with nothing.

I had to find the solution to this puzzle.

I didn't wait for her to do laundry to try again. Few days later, after gathering my courage, I found her setting up the dinner table in the dining room while mom prepared dinner. It was a crazy gamble with high stakes.

Coming from behind her, I simply put my hand between her shoulder-blades and pushed her fairly gently forward over the table. She went down almost compliantly. I kept my left hand on her back to keep her down. She didn't struggle or try to get up. Not a peep left her lips.

She had another short skirt on, and I flipped it up over her lower back revealing a diminutive g-string that did nothing to cover anything.

I ran my hand on her smooth round ass-cheeks enjoying the incredible feel of her skin. I didn't waste much time as mom could walk in on us any minute. I zeroed in on her crotch and rubbed it up and down a couple of times. Abby moaned quietly and didn't resist. I quickly slipped a finger under her g-string to touch her labia. There was some moisture there, not enough to ease my finger's travel between her velvety lips, but enough for me to feel it. I didn't try to penetrate her hole. I aimed for the little button at the bottom. I found her clit and gently ran the tip of my finger in circles around its tip. More muffled moans escaped her lips and I felt her shiver.

However, my exploration got interrupted all too quickly by the sound of mom's footsteps heading over from the kitchen.

I removed my finger from its slippery wrapper and straightened Abby back up. I walked away from her as though nothing was happening while quickly adjusting my hard-on so it wasn't as pronounced through my jeans.

"Here Kevin, put this chicken on the table and come bring the potatoes."

"Ok, mom."

Soon enough, the table was ready and we sat to eat. Dad, mom, me and Abby. Each on our usual chair and we had the usual evening small talk while we ate. During this time, I noticed Abby giving me glances that were a bit different from what I'm used to from her. I couldn't figure out what they meant or how she was feeling. Again, she behaved as though nothing happened less than thirty minutes prior.

I intended to talk to Abby, but as soon as she finished eating, she excused herself and got up, took her plate to the kitchen sink and went up to her room. It was my turn to do the dishes and by the time I was done, Abby's door was locked, and the light was off in her room.

I didn't really see her the next day except for a couple of minutes as she was late coming home and again she locked her room.

For a while, it seemed that Abby was avoiding me. I sure couldn't get her alone to discuss anything. So while she didn't resist what I did to her, she didn't want to talk about it.

Her attitude told me that all is not well with her. She's my older sister and while we didn't get along a lot of time, I still loved her dearly; and the thought of what I've done so far hurt her disturbed me.

For the next few weeks, I didn't do anything in particular to pursue Abby. I didn't watch her and didn't seek to catch her in disadvantageous positions.

But it all changed when I overheard a bit of a conversation between Abby and mom.

I had left my bedroom and was going to the living room, a path that goes by the kitchen, when I heard mom talking to Abby.

"What's with you and laundry these days? It seems that you're doing it every other day."

"It's nothing. I just prefer to have all my clothes clean. A month ago I felt like wearing my blue top to cheer myself up, but it was dirty and it didn't help. I guess I just want my clothes to be always ready for whenever I need them."

Interesting! Abby is doing laundry often. I wonder why.

So she's avoiding talking to me alone, but she stepped up the activity that started me doing what I did. I had to investigate this.

For the next few days I kept a close eye on Abby surreptitiously.

Sure enough on the second day she headed for the laundry room wearing a thin t-shirt and a short skirt.

I followed quietly and kept my distance. I just watched her for a while. She simply dropped her laundry bag in front of the washer and bent over at the waist and started to load the clothes into the washer very slowly. She could have simply dumped the bag's contents into the washer in one go and be done with it. But she was making the process last way longer than it would normally.

So, as not to disappoint, and to clear up things for myself, I walked quietly into the laundry room and as soon as I was few feet behind her, Abby's motions slowed down considerably. She must have felt my presence.

Without hesitation this time, I simply reached for her ass as soon as I was close enough. I didn't waste any time and cupped her crotch. No panties! My cock reached its full hardness, one close to tempered steel, in less than 4 seconds flat.

I felt Abby shiver the moment I touched her flesh. She put both hands on the bottom of the washer's open door and supported herself, then locked her knees with a short distance between her feet.

Now I was sure that this is not something she doesn't want, and that I haven't really hurt her in the previous incidents. She was now ready for whatever I wanted to do.

So with a more confident spirit I lifted her skirt to reveal the little parts that were covered and explored her most private parts.

I ran both hands around her full cheeks. Her skin was soft and covered with light fuzz. It felt so erotic to caress her. I didn't do that for too long as I was mostly interested in her action parts. When my right hand finally reached her pussy again, plenty of lubrication announced her arousal. Awesome!

I had a feeling that I didn't have much time, so I went for the most effective technique that I knew of. After lubricating my thumb and index finger between her wet lips, I quickly inserted my thumb into her hole aiming for her g-spot. Once I felt the rough folds of her g-spot, I pressed down on it and curled my index finger to cradle her clit on the outside. Abby emitted a very audible gasp and whimpered.