A step-mother's job is to make you feel better, and your warm sticky cum leaking back out proves a job well done. Now just pray she doesn't get pregnant.
Do you stop her once her clothes start to come off, or do you succumb to your primal urges and feel how wet and tight her slit is for you? Fuck it. She is technically not even directly related to you.
The problem is once you feel how warm, wet and inviting their fresh teen tight pussy feels, you can't bring yourself to pull out. So, you explode every last drop of potent sticky cum deep inside her. Now just pray that she doesn't get pregnant.