Ren and his four sisters Ayane, Yuuka, Reika, and Sakuya all live together after their parents abandoned them. Old enough to care for themselves they become closer as they care for each other along with childood friend Akari who attends school with the siblings and checks up on them every day. Without parents to care for them they began a daily routine of skinship that involves lots of kisses. Day after day the sisters ask their brother for more intimate kisses that often leads to more perverted acts and it starts to get dangerous for Ren. Finally while kissing Ren, eldest sister Ayane crosses the line and pushes her brother's penis inside. From then on all the sisters start having sex with Ren each day to keep from being left behind. Fearing Ren will fall for his sisters childhood friend Akari confesses her love for Ren and expresses her desire to become a couple.