You and your step-mom have always been very close, probably because you never stopped sucking on her tits. You both find it to be perfectly normal and way too cozy to stop just because the norms say so. Step-Mommy knows you get super horny sucking on her big, heavy, natural tits so she asks if you want her to wank you while you play with her tits, of course you say yes! And step-mommy gets so horny when you're sucking on her breasts, she can feel that tingling sensation travel down to her pussy. She can feel you're getting close to coming, but she wants to control when you're allowed to cum. She'll count down for you...