The stealthy love story of his brother -in -law and his wife Saeko Matsushita, when his wife was busy working for 4 days, she brought her sister home to cook rice to help her husband (very thoughtful). But no doubt that outsiders worried about eating and drinking are still worried about sex for a healthy younger brother, both of them have sex with each other continuously for 4 days until her younger sister came home without even knowing that she had been horned by her own sister.