She lets you grind

Joanne does not seem to mind what you are doing. Apparently, as long as there is no physical penetration, it is okay for you to rub, so she simply allows you to grind against her thigh as you suckle on her breasts, burying as far into her as you can. It is almost as if you are a parasite, attached to her and never letting go. Of course, Joanne locked you against her, so perhaps it is the other way around.

Regardless, you feel ashamed but also incredibly lucky. No mother would ever let her son or stepson do this kind of thing. It has to be borderline incest. Still, you cannot feel TOO guilty.

It does not take you long to finally cum into your diapers. Your stepmother feels it, too, and figures it is a good enough time to stop.

"Looks like I have to change someone's diaper," she muses

You unlatch her breasts and grow embarrassed. Of course, she knows that you came, although you had hoped she would simply ignore it just as she had ignored your humping.

"Um... this is...," you mutter.

Joanne raises her hand, stopping you from continuing. "Sweetie, it is okay. I know that you are still a teenager and get horny. Just as long as you wear your diapers and don't make a mess on me, I'll let you hump me. And don't worry about your father. This will be our little secret, okay?"