I read this one a long time ago and I can't find it even though the tags should be easy… I remember reading two separate entries/chapters. The first one I read was a about a guy who bangs his female friend (I think she had the hair styled similar to cat ears and her hair was light, maybe blonde) in his birthday, he has 2 other male friends who push him to do it. Overall wholesome vanilla work.
Imagine my shock when I found out that this chapter was a sequel of another work where the dude and his 2 friends gangbangs the same girl 😂, all conventual and like it was the natural thing to do, so it looks like it wasn't vanilla at all and it was just a case of a friend group being sex friends, later there's another girl (dark haired, maybe black-haired) that is part of the friend group (I think) who also joins and they have a fivesome. I think she was spying during the first scene.