It was a typical day in the Ben 10 universe, and you and your girlfriend, Gwen, were patrolling the city in search of trouble. You were flying through the air, Gwen clinging tightly to your side, when suddenly she spoke up.

"Hey, can we take a break? My butt's starting to go numb from all this flying."

You chuckle and gently set her down on a nearby rooftop, giving her bottom a playful squeeze as she hops off your arm. "Aw, poor baby needs a break already?" you tease with a grin.

Gwen shoots you an exasperated look, her green eyes sparkling with amusement despite her mock annoyance. She stretches out her arms above her head and arches her back, working out the kinks. "Yeah, well, I'm not used to this whole superhero thing yet. Maybe we could just chill for a bit?"

You consider it for a moment before nodding. "

Gwen's expression instantly brightens at the idea. "Ooh, I love that game! Okay, you go first." She crosses her arms over her chest and leans back against the rooftop wall, watching you expectantly.

You grin, feeling a bit proud of yourself for thinking of such a fun game to play with Gwen. "Alright," you say confidently, "I can hold about... sixteen loads in my stomach at once."

Gwen raises an eyebrow, a mischievous glint in her eye. "Really? That's impressive," she murmurs before slowly walking over to you. She stands close, so close that their bodies are almost touching, and looks up into your eyes. Then, carefully but deliberately, she reaches out and wraps her fingers around the base of your hard cock.

"Mmm... feels good in my hand," she whispers, slowly beginning to stroke you up and down.

Gwen's breath hitches as she continues to stroke your length, her other hand sliding between the two of you to feel how wet she is. She bites her bottom lip, fighting back a moan before finally relenting and giving in to desire. With a swift motion, she pulls down your pants and boxers, revealing your hard cock fully exposed.

"There," she says breathlessly, "that's better."

Gwen takes a step back and looks at you expectantly, her eyes still fixed on your cock. Her hand slides down to her ass, parting the cheeks as she spreads them wide. "Come here," she purrs, beckoning you closer with a single seductive finger.

You can't resist the invitation; you move forward and position yourself behind her, your hard cock pressing against her entrance.

Gwen lets out a soft moan as she feels you press into her. She's been wanting this for so long, ever since you revealed your alien powers and that huge cock of yours. She arches her back, offering herself up to you as an invitation. "Fuck me," she whispers, knowing it's what both of you want.

You thrust your hips forward, impaling yourself on her tight ass, feeling the heat and wetness envelop you completely.

With each thrust, Gwen's body meets yours in perfect synchronization, her moans mingling with the slapping sounds of your hips against hers. She can feel you growing inside of her, filling her up with your alien seed. You promised not to cum for a while yet, but it's becoming increasingly difficult as she tightens around you, milking your cock with every movement.

"One..." she gasps out between thrusts. "Two..." Her words are breathless and full of desire. "Three!"

Gwen's cry echoes through the rooftop as your hot load floods her insides. Wave after wave of thick, potent semen pumps into her, coating her walls and spreading deep within her core. She clenches and unclenches around you, reveling in the sensation of being filled by you.

As you finally finish, Gwen collapses onto the rooftop surface, panting heavily. She rolls onto her back and spreads her legs wide, showing off the evidence of your climax leaking out of her. "Mmm... damn, that felt amazing," she sighs contentedly. "