My twin sister and I became closer than ever (PART 7)

For reminder, I'm M20 and she's F20. I previously said that I kissed my girlfriend following my sister's teachings, and my gf loved every bit of it.

Things are slowly going good, maybe even too good that I start asking questions to myself. I really love my girlfriend, I don't want to lose her but at the same time, I hate not telling her I had an affair with my own sister. Then I'm thinking ... it was just making out, it couldn't get worse, right? Well I was wrong!

Approx. 2 weeks later after I had kissed my gf, I had very bad sexual urges / desires. Parents were away for plenty of time, it was only me and my twin sister. And ... she gets very comfortable. Like super comfortable. I must confess, I had to j* off twice to three times a day whenever my sister was around. She would NEVER wear pants, only a super small piece of thong covering her kitty. Her two wide thick butt cheeks were clapping at each step and it kept driving me crazy. So, to eliminate those dirty thoughts of mine, I waited she would stay still (like when she was cooking for us in the kitchen), I stayed near the sofa and started edging at the amazing view. After shooting the liquid, I felt the usual regret and could move on ... but only for about an hour.

One time I couldn't get a clear vision of her, so I got to my room, put on my phone screen a photo of her ass in a bikini when she was laying on her stomach and started my little thing. I was really lost enjoying the moment, so lost that I didn't even realize she was watching me j* off to a picture of her. I got super nervous and scared

She just blew me up a kiss and left with her butt cheeks clapping. She even bent over right at my doorway to retrieve literally nothing, she's such a tease! But I'm so glad she wasn't angry at all over the fact I had my penis in my hand for her.

(Part 8 later)