Step daughters/Asexual/1st Wednesday/play here/see/show/continue
Sandra's hands are shy away from your penis ... but not very far. Her face is still quite close and Masha is looking at it not knowing what to think.
You: "Now now you are not supposed to know that so don't repeat it, but boys like to play with it like this" And you start to stroke yourself gently. The two girls look fascinated your skin going above your shaft and back.
You barely do it for a few seconds and don't even have the time to propose that Sandra asks you, adorable
Sandra: "Can I try to play with your pee-nus?". You see Sandra very curious and Masha weirded out and frowning but with a smile and blushing hard.
You: "Ok but you need to keep it a secret. Masha you'll help her keep it secret, right?" Masha nods shyly.
You: "Come on, you can touch now" and you place one of Sandra's hand on your dick. She spontaneously places the second one as well and starts to try to stroke.
She is a bit clumsy and clearly does not know how to do it (shockingly so, what do we teach our 4 years old nowadays!) so you put your hand above hers and help her masturbate you.
Masha comes a little closer.
Sandra, shocked: "Hey it got bigger!" She removes her hands and smells them, frowning a bit.
You: "Yes, that's what happens when a nice girl plays with a boy. It means you are doing it very well".
Sandra smiles to the compliment.