Rebecca got out of the car and walked up to her boyfriend's .. (OnlyFans)

Rebecca got out of the car and walked up to her boyfriend's apartment. Her boyfriend greeted her with a deep passionate kiss while squeezing her meaty asscheek before letting her inside. Mark sat silently tasting the aftermath of his sexual adventures with his unaware sister, snuggly on her clit as the two giants spoke above him. He heard only faint words as his sister Rebecca told her boyfriend about her new toy. Over time Mark began to smell his sister's sex come alive, with the Faint sounds of lips smacking together above him. Before he could even think, light flooded into his panty prison as Rebecca's gigantic boyfriend smiled down at the tiny clit ring. Hot breath washed over Mark, smelling traces of pot and Cheetos. Mark braced himself as a large tongue came down and began to eagerly pry at his surroundings. Mark screamed internally as waves of pleasure went through his piercing form. 
Covered in saliva, Mark watched as a massive nose approached and the loud sound of wet slurping and distant moans filled his ears. He cried again in silence as he wished his hell would end, having to watch his sister be orally pleasured. Hot breath came and went as the massive nose hovered above Mark when suddenly the nose lifted and the tongue approached once again, this time for a brief moment before leaving all together. Mark sighed in relief thinking it was over. However, replacing the nose and tongue was the most giant hardest dick Mark had ever seen. The sight made Mark freeze in fear as it hovered over his tiny form before slamming into the lips below and thrusting a mound of public hair into Mark's surroundings. 
Mark cried over and over as the deafening slaps of skin-on-skin contact echoed around him. Wet squinting and slurping sounds below him, moans above, and the sight of public hairs and skin rushing at him sent Mark into a state of pure agony.
The muscles around him on his sister tensed as Rebecca screamed above marks head. A few more pumps slammed into his world before the head of the massive dick re-emerged once again. Pulsating, red in color, Mark could hear something rushing towards him, like a raging waterfall! He screamed out once again as floods of semen washed over his piercing form and surrounded him. Gagging and screaming as the salty bitter taste washed over his tiny body. 
Rebecca cleaned her brother of a load of semen hastily before cuddling for some time, allowing Mark all the time in the world to taste and experience the leftovers of her lovemaking. After some time, Rebecca told her boyfriend of the amazing things Mark's new form did, turning him into a dildo once again. However, after looking things up, Rebecca's boyfriend was able to add to Mark's abilities and transformations. Mark felt another large wave of pleasure go through him but he took his newest form, a brand new pocket pussy!
Rebecca and her boyfriend kissed hard above Mark's new form as he was lubed and hovered over the awaiting massive cock that drenched just hours before. Mark was slowly lowered to the head of the cock, rubbing the tip in a small circular motion before he was thrust down hard. The massive cock filled every inch of his hole, causing Mark to scream in pleasure, as he sat at the base of the throbbing cock, he was feeling intense waves of pleasure. The pleasure began to increase as his sister stroked the cock in him with Mark's form. He felt disgusted and secretly craved more... the taste of latex, lube, and sweat mixed with leftovers of the two giants' earlier sexual escapades, causing Mark to gag. He hated his sister and himself for putting him through all this, if he didn't mess up the address he could have had all this "fun" with his girlfriend. His thoughts of course were cut off as he felt the cock throb hard inside him before it once again erupted. This time it filled his sex toy form as Rebecca drained the cock with each stroke. His taste buds exploded with disgusting salty flavors before he was pulled from the cock and dropped onto the floor, where the semen drained from his hole as the two kissed more and continued above him...

End?