OBA-101 My little sister's tutor Sayuri Obasan Sayuri Naiinu

"I want you to tutor my daughter, Haruna, who is preparing for exams." Sayuri agreed to become a tutor at the request of her brother Ichiro. Meanwhile, there was one man in high spirits. That was Haruna's brother, Shinya. It was five years ago... Shinya, who had also been tutored by Sayuri, couldn't forget her intelligent profile even now. One day, his affection for his aunt was seen through by Sayuri. Then, Sayuri took an unexpected action towards Shinya...