Starring the number one ideal big sister actress, Ichika Kamihata! A younger brother's twisted desire to "have sex with my sister" finally reaches its breaking point. One day, he accidentally catches a glimpse of his sister having sex. Seeing her erotic side for the first time triggers an uncontrollable sexual urge. As his lust intensifies, his sister is left bewildered. But what action will she ultimately take? A taboo incest story!