血の繋がりのない妹と二人っきりの3日間！ここぞとばかりにセックスしまくった！！　松本いちか (2022)

Overview

My mother remarried and I now have an older brother who is not related to me by blood. At first, I was worried about whether I would be able to get along with my brother, but now we have gotten along so well that our relationship is more than brother and sister! Normally, I would steal away from my parents and have sex with my older brother, but my parents were going to be away from home for three days for a memorial service... I'm really looking forward to spending three days alone with my brother!