Account from Stella, 18 years old.  
Mr. Campbell was very kind to me and asked me not to undress right away.  After offering me a drink, he suggested a "game." I agreed, and he took me to the bedroom of his daughter Jenny, who was in swap with my father. There, he asked me to undress with the door closed and put on his daughter's undergarments, which had been laid out on the bed.
It was easy because Jenny and I both have small bra sizes. I was surprised to see that the panties had been worn, but they weren't dirty, so I put them on anyway. 
According to Mr. Campbell's game, I was supposed to lie on the bed, face down, pretending to be asleep, and let him know that I was ready. That is what I did.
 
He came in, sat on the bed, and began to stroke my hair affectionately; then he moved his hand down my back until he was caressing my bottom over my panties while bringing his mouth close, kissing my neck tenderly, and whispering into my ear: "Don't worry, my girl; everything will be fine..."
His caresses moved between my thighs, and he kept kissing me as he unhooked my bra. Then, he gently turned me over, and I could see that he was already naked and had a firm erection.  I assumed he would force me to suck his cock—like all the others—but he didn't.
He pushed aside the bra and began kissing my little tits, delicately licking my nipples, and sliding his hand down my belly until he was caressing my pubic area beneath his daughter's panties, saying: "Relax, my girl, don't be afraid, trust me..."
He did all this with his eyes closed, and at no point did he try to kiss me on the mouth. Clearly, his "game" was an erotic incest fantasy, and in that moment I was his daughter Jenny, so I decided to stay silent for not break the spell.
He moved slowly downward, kissing my belly as he pulled off my panties, then plunged his tongue into my wet pussy, savoring my juices and preparing me for penetration...
I was already very aroused and stimulating my own nipples when he placed his hard cock against my vulva, saying, "Don't be scared, my girl; I'll go very slowly so it doesn't hurt, and in the end, you'll enjoy it..."
And so he did. He positioned himself over me and entered slowly, holding me the way one might hold a daughter. I was very wet, and with just three gentle thrusts, he had his entire member inside my tight pussy, all the while kissing my neck and whispering, "I'm not hurting you, am I, my love?"
He was fucking me and kissing my tits with his eyes closed, and after we'd been fucking for just a minute, he asked me, "You like it, don't you, my princess?"
Then I brought his daughter's panties close to his face so he could smell them, while whispering into his ear, "Of course, Daddy." Upon hearing those words, he climaxed instantly with all his might—thrusting again, and again, and again—until he had emptied his balls inside me... though, in his own parallel reality, he was emptying them into the vagina of his beloved daughter, Jenny...
What happened during the next six hours of the exchange was a very different story—one that I have only told my father, as I usually do after every exchange...