Zāko na Shimai to Suyasuya Ecch

The main character has two younger sisters. The younger sister, Riona, is energetic and is currently at the peak of her rebellious mood, opposing the main character. The older sister, Shiori, has a calm personality and has been rebelling against the main character for over a year. In the past, Riona and Shiori followed the main character everywhere, no matter what he did. Even now, the main character still cares about them and wants to restore their former relationship. One day, the main character's thoughts change dramatically when he sees porn that he borrowed from a friend. The porn he borrowed was about younger sisters, and he began to see Riona and Shiori as women. The main character sneaks into Riona's room, where she is sleeping, and slowly reaches out to touch her.