Sibling Secret

I'm just hanging out in the living room watching TV when my sister comes in the room in a bikini! I had no idea she was even here. She came running up and hugged me and asked if I wanted to go swimming, but seeing her in that bikini... I had to go in my room for a little bit and just get myself off. I couldn't believe how hard I got just from seeing her in a bikini. In the middle of me jacking off, she bursts into my room!! She knows.. she knows I fantasize about her. I can't believe how nonjudgmental she is about the whole thing. I also can't believe what happened next..