I, Yonezura Keita, have just reunited with an old friend, Noboru Sasaki, for the first time in several years. Noboru has a cute and attractive girlfriend, and her name is Sana Otonashi. I fell in love with Sana, and decided to take advantage of the opportunity and start cuckolding. As he continues his physical relationship with Sana, he gradually comes into contact with Sana’s younger sister, Saya, and Sana’s older sister, Sarina.