My cute sister sucking a cock and getting fucketd

My sister and I have been very close since we were kids, and I'm kinda close to her best friends too and know some of her schoolmates, etc.
We're in high school, she's one and a half year younger than me.

She's a kind of quiet girl, you wouldn't expect anything dirty from her, I do always realized that she was beautiful and realized when she was developing a nice ass and nice legs but never thought anything sexual of her. Always saw her naked or in underware like most families do, no big deal.

One day, one of her best girl friends told me that she was planning to fuck later that week, it got me totally inadvertent, it was so unexpected from my little sister! even for me! having such good close friendship. I couldn't believe it, didn't want to believe it, the fact that my cute little sister, the one I helped to walk when she was a baby, to talk, and all that, was going to get fucked by an idiot that I didn't know!
It might be normal if you see it from an external point of view, but not for me, she was the treasure of the house! everyone trying to take care of her.

At first I wanted to ask her, and tell her that I wasn't going to allow it at all, but then it made me really really horny, after all those family thoughts, just thinking about it made me hard, made me dream about her getting fucked by a guy she barely knew, enjoying her (even acknowledged by me) beautiful thin-but-tasty body, big beautiful ass and killer thick legs, got all my incest fantasies I didnt know I would have at 100%.
I waited 'till she came back from school that day and we talked about ourselves but she didn't mention anything about it, but i knew it was true because her friend never lied to me or to her. It was the first time I was thinking sexually about my little sister, and It started to make me hard to see her in school outfit. I jerked myself with that thought the entire week untill the weekend.

On Friday, she was getting ready "to hang out with friends", yeah! right.
It was still early and I catched her going out of the bathroom to get dressed in her room and I saw her in extremely SEXY underware, as I said before it was normal between us, but I was getting horny with her so I enjoyed watching her, and asked her were she was going and she said to hang out with a few friends (while watching/testing mini skirts and tiny shorts in front of the mirror What a cinism! but it made me very hard. The sight of my little sister being a sexual character! wanting to touch a hard cock, wanting to be sexy for a guy.. made sooo horny.)

Next day I asked her best friend what did my sister do last night and she told me everything in detail:

They started making out, then he was touching her legs, at first very soft but then very roughly, she liked every second of it, then she started grabing his bulge but quickly he took his penis off so she could grab his hard on in it’s entirely, her friend says that she saw them since she was with other friends close to her, she says he had a big big cock with a big juicy head and that my cutie sister loved stroking it, it was certainly the first time that my sister touched a cock, but, her friend says that she got very expert after a few minutes of handjob, the guy was loving it, I couldn’t believe it but i couldn’t deny how sexy it sounded. Then he took her shirt off while bouncing his hands over her breasts, he took her bra off also and was touching her tits very soft while moaning, he started pushing her head against him so she could get his cock on her mouth, at first she was a little reactive but since she's an obedient girl, he knew how to convince her, so she took his hard cock on her cute mouth and sucked it very slowly while playing with his balls, she also licked its tip without concern. I just couldn’t believe what I was hearing, my sister? If she wanted some toy I could bring it to her so she can play or something, but a cock? Such dirty thing full of hair and all that? And she wanted it whitout presure to put it between her soft virgin lips and suck it and lick it? It was so confusing for me!

Then they took the rest of clothes off, she was totally naked, and the guy licked and smelled her virgin pussy a few minutes before putting her doggystyle and fucking her like a bitch, after some time fucking, he told her to get on her knees to suck his cock again, she did it like a good girl, she loved getting on her knees in front of him, then he pulled his cock out and came very hard over her beautiful, gorgeus cute face, it was all covered in cum, my little sister’s face! Oh my god!

After all that her friend told me that if wasn't surprising for her, all my sister talked about previous weeks was about worshiping a cock, grabing a cock, licking a cock, licking its shaft, etc

I was very pissed off but a few days later I told her that I knew it all, I knew that she was a bitch and what she had done, she told me not to tell our parents, she'd do anything if I keep the secret, so I said: Ok, but you'll have to suck MY huge cock, bitch!
So she did it, it's really good to cum on her pretty face, she've been getting a better cocksucker and now we're having full sex including anal, her ass is so tight and so cute!

I enjoy it all the time now, so it wasn't so bad to know that she was a bitch.