Grope her tits.

'I've gone this far, I won't stop now', I thought and went to grab her breasts. I managed to get both my hands on her gorgeous tits. They were incredibly soft and also warm. The feeling of caressing my sister's breasts sent a wave of sensation through my whole body and brought my dick to full attention.

I moved my hands in circles around Cassie's nipples, ever so slightly touching them. Every now and again I gave her tits a light squeeze, satisfying my new found lust for her body.

After a while I grew bolder and played with my sister's nipples. I pinched them and let my fingers dance on them.

My sister didn't seem to be bothered by that in her sleep. Her breath wasn't changing and she didn't shuffle again.

This whole experience made my lust for my sister's body only stronger. I wanted more. But how would I get away with that? Anything more and she was sure to wake up.