It's been two weeks we are dating, M and I, she woke up in my bed once, i woke up in her bed twice.
She sexted me in the morning and I crash by her place in the end of the day, she introduced me her little sister.

What about her sister, S, she is young, nervous, obsesive, unconfortable.

After dinner, I helped with the dishes, taking the opportunity to grab her butt for the third time.
We kissed, we danced, we walked to her room and she pushed me on the bed and got over me to kiss again and try to undress me while I try to undress her.
oddly she dont let me undress her and she pulled my pant and start touching me with intent.
then i got myself tied to the head of the bed.
because her head was close to mine, we are kissing, i didnt see that it wasnt her hand that grabed my junk, but I quickly realise went new lips touched my hazlenut.
my girlfriend pull herself away, still in her clothe , her sisters was naked and sucking my dick like if she craved for it.

i am embarrassed, shocked, ashame of my own excitation. my now considered crazy girlfriend ligth a cigarette (what the hell, i though she was a non smoker) 
and begin to tell me :
girlfriend : my sister is more important than anything else for me.
             she suffers from nymphomania at a point its dangerous for her.
             she need a good lover who will take care of her need
             without treating her like a sex toy. as you noticed i dont
             have a great sex drive, once a month is enough for me, but
             my sister need sex to feel normal.
as she lecture me about why she whore me to her sister. the later stoped sucking and sit on me on the cowboy position , this is how i felt her inside for the first time.
girlfriend : i know you need the romantic part and i kind of enjoy it, but my sisterbis not interrested in preleminary, she need the D. the deal, we date , we cuddle, we dance , you fuck her and sometime me...

{closet A long time ago when M was a yougn adult but still live at her parent, she had an outer town friend who came to visit her, they were not lover, but he cared a lot about her because she came out of a difficult relation and her friend, B, helped her a lot in the somewhat violent breakup. They spended the whole day together and they flirted, "I date someone" she said, and he apologised , "But he havent showed me any interrest yet", and she kissed him. "I dont think we should form a couple" he said while still holding her ankle. "Maybe just tonight without thinking about tomorow". And they maked out. They entered her parents house and directly into her room, into her single bed, and then into herself as they are making love. They werent done when someone entered the room. It was her sister who just got out the shower wearing nothing but a towel under her arm pit like a dress. "C is here!". M pushed me away, "What ?", "He is comming in your room right now" she followed. As M got on her feet saying "Fuck!" repeatly, her sister pulled out her towel and covered the naked body of M and them pushed me in the closet, and finally entered the closet. That was quick thinking, really quick but now I am locked in the closet with her naked sister, a closet to tight to avoid skin contact. 
B looked in a crack to witness M with her maybe future lover, it was a dude taller and stronger than who looked at her in a towel with love and desire. M was about to say something but C hugged her declaring his love. He lifted her from the ground and let himself fall in her bed still warm from B passage.
B was feeling stupid, watching another guy taking his turn on his one night from the closet, he would certainly felt gross if he was at his place, best if he never knew. B almost forgot he was skin to skin with an unknown woman but when she started to touch her self while watching M getting pounded. B asked himself how the hell he ended there. He wanted to run away but he certainly didnt wanted to spoile her chance with this men. It was clear for B that he didnt love M the way of a relationship but as a someone he want to make happy. 
The unknown girl grabed his bone who started to releave and started to pump him using M juice whom covered the thing as lubricant. B let it happen, he was afraid and then excited.
}