The film tells the dark corner of the lewd woman Kasumi with her brother-in-law. The love affair between the two occurred on the day his cock stepped into his brother's home. The brother just blurted out that the two had chatted and flirted with each other, and the two words "lewd" were clearly visible on his sister-in-law's face. She constantly has sexually arousal and seductive actions that make her brother unable to restrain himself from such a juicy invitation. While his brother was not noticing, a clumsy incest affair took place very quickly between the two.