I can’t remember the name of the erotica but this is the general idea of what I remember it being about:
BF and GF in school together they are both long time partners and are both virgins, a new student comes to the school, this new student seduces the gf (helped by the gfs best friend encouraging it) eventually the BF GF and GF’s best friend hangout with the new student the gf gets fucked by the new student in another room while the bf listens and ends up fucking his GF’s best friend.
I hope that makes sense if anyone can help find it that would be appreciated