Ali looked up with the hottest "fuck me" eyes I'd ever seen, and then she stuck out her tongue and licked the head of my penis, which was wet with a mix of my pre-cum and her saliva.
I watched as she smiled and opened her mouth, just enough to take the head of my cock in between her lips.
She grabbed my hip and pulled me with her as she rolled onto her side and spread her legs, raising one of them so I could watch as she fingered herself while sucking me.
I felt my balls beginning to tighten, felt the familiar tingle sweep through me as I headed toward orgasm...
And woke up.
Ali licked her hand, wrapped it around my swollen penis, and began pumping me again.
"Ali,..."
I reached for her, sliding a hand under her, my fingers curling against her back as she pushed me steadily toward the brink.
"I'm gonna cum..."
My cock erupted, spewing semen all the way up my chest, almost to my chin before follow-on bursts coated my stomach, pooling as she drained me.
"Wow," she said, giggling. "You came a lot."
"Uh-huh." That was the best I could do. I was suddenly out of breath, and I couldn't for the life of me put two words together.
Ali dipped her head down and began lapping at me, scooping my cum up onto her tongue like it was drips from an ice cream cone, and when she'd licked me clean, she bent at the waist, swallowing my still throbbing phallus and sucking it to get every last drop of cum.
I closed my eyes and moaned; man, did that feel good.
Ali pulled her lips from my suddenly deflated dick and rubbed my belly with the flat of her hand.
"There. Now maybe you won't be hard as a rock when you get to Lisa's."
We were a week and a half into the second summer session and I'd spent more time naked at Lisa's than we were used to. My schedule allowed me more free time than did Ali's, and Lisa had been able to start satisfying her urge to draw me naked.
Maybe I should be more specific. She'd been able to satisfy her urge to draw my penis.
I'd never been with a lot of girls, but I'd definitely never been naked around one so much, not even Ali, where she was so close I could smell her; so close I could feel her breath; so close my cock seemed to gravitate towards her.
And she never touched me.
Each day, by the time Ali arrived, I was so hard my balls were beginning to hurt.
Today would be the day Lisa put the final touches on a sketch we'd been working on since Monday. It faded in about mid-thigh and back out again just below my ribs. The mid-section, though, was solid with detail.
After Ali arrived, we'd continue with a pair of sketches that Lisa hadn't named yet. One featured Ali on her knees in front of me as I thrust into her mouth. The other had me on my knees with my face buried between Ali's spread thighs.
Lisa didn't have a name for them yet, but Ali and I called them the "Head" sketches.
The first day Lisa spent 'doing a study in charcoal' of my cock, I was throbbing and ready to burst when Ali finally showed up and took off her clothes.
In a moment of inspiration, Lisa coached Ali as she kissed, licked and sucked on me. She coached me, too.
"Fuck her mouth, Tommy. Like this."
By that point, Lisa was naked, too, and leaning against the wall beside me. I watched as she reached down and grabbed the head of the person she imagined was going down on her.
The rest was almost instinct.
Ali clutched at my ass as my fingers wound into her hair and I thrust my raging member in between her lips and across her tongue.
And she sucked me.
And I came.
Hard.
I swear it felt like someone reached inside me, grabbed my balls and squeezed, trying to milk the cum out of me.
And suddenly, out of breath and weak in the knees, I understood why Lisa had told me to lean up against the wall.
We'd spent most of the week replicating that scene, alternating between Ali being on her knees in front of me and me being on my knees in front of her. A lesson quickly learned was that Ali liked pulling me against her as much as I liked her doing it, but she couldn't take much of me going down on her while she was standing.
Lisa quickly adapted, and to be honest, I couldn't tell you which I liked better, the sketch with Ali standing or the one where she sat with her legs spread holding my head against her.
I enjoyed going down on Ali when she was sitting with her legs spread, thighs draped over my shoulders.
Now, though, it was Thursday.
Lisa and I had a solid two hours alone before Ali got out of class.
My cock twitched.
Two hours of Lisa studying and drawing my swollen member.
And then Ali would make me cum. Again.
The morning flew by and soon I was knocking on Lisa's door.
"Just a minute." I could just hear her muffled voice through the door.
I heard some shuffling behind the door, and then it cracked open.
"Come on in," Lisa said, peeking her head around just enough for me to see her, and as soon as she closed the door behind her, I could see why she was trying to stay hidden.
She was all but naked, fastening the lower buttons on an oversized man's shirt, closing it just enough to cover herself.
"Time got away from me," she said, her breasts swaying beneath the cloth as she rolled the sleeves up and stepped off toward the kitchen. "Help yourself to anything in the fridge. Give me about five minutes and I'll be ready to go."
I followed her past a table she had set up and looked down at the sketches she was working on.
One sat behind it on the floor, resting against the wall, ready for framing.
"I sold that one," Lisa said, walking up behind me.
"You sold it?" I was a little stunned, and Lisa almost knocked me over when she slid a hand inside my arm and brushed against me.
It was one of the more intimate portraits of Ali that she'd done. Ali was laying back, her legs spread, one arm stretched overhead, the other by her side, the fingers of her hand laying just inside her thigh, brushing against her pussy. Her breasts, gentle mounds atop her chest, were crowned by puffed, erect nipples.
And the look on her face was pure euphoric ecstasy.
Most shocking, though, was the fact that I could recognize it as being her. If I'd stumbled across the portrait anywhere else, with the body covered and only the face exposed, I'd still know it to be my sister.
And soon, this image of her nude and enraptured would be hanging on someone's wall. My cock began to swell, pressing out against my shorts.
"Yeah. I sent digitals of some of the sketches to my agent and he's been getting a lot of response to them. In fact, I think I can sell two or three more just like this one."
I swallowed hard, my cock swollen and erect, throbbing at the thought that my sister's body would be on display for complete strangers.
"The same buyer is supposed to let him know later this week about a couple of the sketches of you and Ali together."
I started taking my clothes off. My cock swayed in front of me, and as I walked back toward Lisa's work area, I stopped to look at the sketch of Ali again. My cock surged to full hardness again.
I couldn't help myself; without thinking about it, I wrapped my fingers around the swollen shaft of my penis and began to stroke up and down.
"You can't take your eyes off of her, can you?"
I looked away from the picture as Lisa stood next to me. I looked back at the picture and shook my head.
"She's really beautiful," Lisa said.
I nodded and my heart skipped a beat as Lisa placed her hand on my ass and leaned in against me. l looked over at her as her other hand reached for me, her fingers almost covering mine as she touched the throbbing head of my penis.
"Don't waste this."
Her fingers slid awkwardly over mine, trailing down until her fingertips were cradling the bare skin covering my balls. And then they were moving up again, grabbing at my fingers, peeling them away, freeing my phallus.
Her hand replaced mine, flat against me as she pressed my cock in against my body, and rubbed the shaft with the heel of her hand.
