Hello all,

I'm looking for a name of a manga I read a while ago (at least three years ago), and despite my best efforts, I am unable to find what I am looking for, so I was hoping for a bit of help. I guess I'll just post what I remember about it.

Older sister and younger brother have a sexual relationship. The sister is trying to help her brother sexually because he is inexperienced, and he has an inexperienced girlfriend, but they don't really hit it off, as it were. The sister has friends that tease about corrupting him and having sex with him, which they eventually do. In one of the chapters, she is either forced into sex or just gang banged in the park, but her younger brother finds her and they have sex after.

I remember it being about 3-4 chapters. Thank you for looking, and sorry for the vagueness, but that is all I remember about it.