Gifu to shimai: Momojiru ajikurabe(義父と姉妹 桃汁味くらべ)

Ayaka, a former president's secretary, was married to her son Naoki and had a happy day. One day, when Shinsuke, the president and father of Naoki, was injured and was in need of nursing care, his feelings for Shinsuke who was sleeping inside her and Naoki began to shake. And nursing care will eventually be forbidden sexual care. Ayaka's older sister, Reiko, who lost her job due to the recession appeared there...