Alright, sis let's see what you can do

"Oh yeah that's it sis , show me... show me why I should think you're the best"

She smirks, starting to stroke your cock even faster than before. “Oh yeah? You want to fuck my tits?” Grace's words catches you off guard, causing you to freeze for a moment. You can feel the heat building up inside of you, but you try to hide it from her. The last thing you want is for her to get an ego, but you just couldn't resist when you said.

"Fuck yeah..." You muttered under my breath before coming back to your senses. "I mean fine.... whatever. Guess it'll help me decide if they're real.." Grace looks at you with a mischievous grin, her eyes sparkling with excitement.

She smirks, continuously stroking faster and faster. You watch in awe as your sister's fingers dance around your shaft, her touch sending shivers down your spine. As she continues to stroke your massive member, you can feel her grip tightening around it. The heat between your legs intensifies as you both lose yourselves in the moment, lost in the sensation. “Don’t lie… you know you want want it!”

Reaching towards her the insides of her breasts, she ripped a hole in her suit, right under her tits. It was big enough to squeeze as much of your hard on inside of her cleavage without suffocating either or.

Grace moans softly as you sink into her, the heat and the pressure sending shivers down her spine. You can feel her body pressing against yours, her breasts pressing against your chest. The sensation is overwhelming, and you can't help but let out a soft moan. You pull out of her, only to have her grab onto your hips tightly.

"No i don't.... I'm just doing this for.... your sake" You say trying to play it off but your eyes still can't keep away from your sister's own tits.

She smirks and lifts her bust a little higher before one hand brought your cock toward the hole in her suit. She smirks and winked at you. “No? Then you don’t want to go to town? Cum in my suit? All over my tits?” She says with a sultry tone. Grace's words send a shiver down your spine, and you can feel your own excitement building.

"Oh fuck..." You take a deep breath and nod, feeling a rush of pleasure at the thought of giving in to your desires. Upon moaning under your breath, your cock throbs a bit in her breasts as she continues to talk dirty to me.

"Just admit it and this could all be yours~" Grace's words send a thrill through your body, and you can feel your heart racing with anticipation. You can't deny that the thought of being with her and having her body is driving you crazy. "Fine i want to... but it's for .... for science sake . I want to make sure I have all the data before I make my decision."

“Oh yeah? Then go ahead… thrust away." She smirks as she presses the tit into her cleavage. "Fuck your slut of sister's tits and let’s see how long you can hold back saying my tits aren’t the best!” Grace moans softly as you begin to pump your hips, feeling her body press against yours with each movement. She leans in close to you, her lips brushing against your ear as she whispers dirty words.

"Oh fuck"

You accidentally let out a moan moan as you push the rest of your cock in between Grace's tits, feeling her tits wrap around my cock feels even better than you imagined it feeling like. You're surprised that she's giving you access to go to town on her breasts, but hey you're not complaining. Just means unlike all those other guys who fantasized being in the exact same situation you are in, you get to have fun with her breasts. Taking a deep long breath to get your bearings together, you begin to thrust your cock, feeling the softness of her knockers hit ever vessel of your cock. "Oh fuck , Oh fuck"