Sorry for being vague as it is kind of old doujin, at least its first 2 chapters. It has 4 chapters overall. The first 2 chapters is all about MC and the petite girl. The last part of chapter 2 is a cliffhanger that MC will have a threesome with their big boob bestfriend. Chapter 3 is mostly threesome, while this big boob bestfriend claimed that it was her first time and really wanted to experience sex, hence, wanting to have sex with MC. Chapter 4 is all about MC and the big boobs girl(No sex for the petite girl).