Watching Him Spurt

So it is that I'm in Chris's room. There is a tension in the air, although the conversation and each other's company is easy as usual.  He's lying on his bed in just his bathrobe. I'm sprawled in an armchair wearing just my panties and a bathrobe. The conversation isn't even sexual, well, that is, the conversation with our voices isn't. The conversation with our eyes is something else entirely.  We are having two distinct conversations here. I'm looking him up and down and desperate for him to get his cock out. He is looking at me in a way that just begs to see up my legs. One of us will break first.  It's me. I let my legs slide gently apart, and he sees my panties...and I hope, the wetness. I see a stirring under his robe, and I know he is getting hard. Our conversation continues uninterrupted. I'm lightly stroking my panties now, and it's making me fizz with excitement. My body gives little jerks, like electric shocks. I'm loving the tension. Chris is fully hard, but dammit, I can't see his cock yet. Finally it slips out into full view. I know that cock so well. I know its taste, and I know how it feels when it's buried deep in my vagina. I know how it feels when it spurts, and I know that sweet sting when it stretches my arse. I also know how it tastes after its been in another girl.  Chris has stopped talking now. We both have. The moment for words has passed. He is slowly wanking himself, and oh....I'm loving it! I have my hand inside my panties now and I'm not going to take them off. Well, maybe I will, but not for now.  My cunt aches. I need to have it filled, but I also know that's not what we need. Chris is wanking faster now, watching my hand move under my panties. I'm alternating between rubbing my clit and finger fucking myself. I reach down and pull my panties aside. Chris can see my glistening wet cunt now, and I see the pre cum running down his cock. I ask him to stand up and lose the bathrobe.  I stand with him, pulling the waistband of my panties down under his cock. He knows what I want. A few more strokes is all it takes and he cums onto the material inside my panties. There's a lot of it and it runs down into the gusset.  Then, because I know what he likes, he lays back on the bed. I straddle his tummy, reach inside my sodden panties and finish myself. I pull the gusset aside just as I cum, and I squirt heavily all over his tummy.  Does he want more? I think he does. I raise an eyebrow as a question and he nods. His bathrobe is tucked up beneath us, so I can do what I know he wants. I put the panties back in place properly. I make sure the gusset is covering my swollen cunt lips. Then I tease him. "You want me to, don't you?" He nods. "You want your sister to be naughty, don't you?" He smiles. "You fucking bitch" "spank me" he slaps my bum....hard.....and again....and again..IT FUCKING HURTS...WHICH IS WHAT I WANT.   Then, I suck my thumb and pee my panties on his tummy. I do it slowly, and I feel his cock stiffen behind me. There isn't as much as I'd have liked to give him, but what is there is enough. I feel his cockhead against my bum, so I pull the material aside again and press backwards.  I kiss him deeply as he enters me, and we fuck like a couple of teenagers. I cum four times before he cums inside me.