My little sister's tutor, Aunt Sayuri

Sayuri is asked by her older brother Ichiro to teach her how to study, saying, "I want Haruna, the daughter of a student taking the exam." Meanwhile, there was one man who was excited. That's Haruna's older brother, Shinya. That was five years ago... Shinya, who was also tutored by Sayuri, still couldn't forget Sayuri's intellectual profile. One day, Sayuri sees through the affection she had with her aunt. And Sayuri then takes an unexpected action towards Shinya...