An Unintended Side-Effect

"Daddy...." I hear her whimper into the sheets. I take a step back, a little shocked at my own behavior, which reveals that she's actively playing with herself through her panties!

"Sarah! What are you doing?!" I shout, confused at what I'm seeing Sarah do right in front of me.

"Daddy... I just can't help myself when I get like thiiiiiiissss..." she says, bringing herself further towards climax, right in front of me. She's playing with her clitoris through her panties, making herself cum, not caring that heir own stepdad is standing right behind her. She squirts into her panties, and I can see the liquid running down her inner thighs. I should avert my gaze, try to stop her, or leave, but my hardon betrays me and I do not look away at her shaking legs and swaying backside.

"Sarah, stop this right now!" I shout, desperate for some kind of escape from this predicament. She doesn't listen, and instead reaches her other hand into her bra, apparently tweaking her nipple. Her fingers slip into her panties and she starts full-on fingering herself right in front of me. It's clear she can't control herself when she gets horny, not in the slightest.