When your perverted girlfriend shares you with her sister

Elina and I were 4th year law students. That year, her 18-year-old sister Ioanna came as a freshman in pedagogy and while we didn't like it, she stayed with us to help their parents. 3of us in a three-room apartment, on the third floor of an apartment building, Thanksfully for us Ioanna wasnt one big pain in ass.
Thanks to Elina I learned everything about sex and sex games. Many times I became her male slut, she would tear me apart with her strap-ons. At first I refused, but later I enjoyed it with super orgasms. I was also making Elina horny because I was moaning like a little girl and victim my pure hairless ass.There were times, of course, when she became my whore.