Hajimete no Hitozuma - 5

The final exams are approaching, so the main character throws all his affairs for the sake of study. Since Kawai, a school whore, is not ready for exams, she asks her friend to help her pass exams with good grades. He agrees to help her, since he will be awarded with sex for such a part -time job.
After several days of classes, the main character remains alone with the mother of Kai. While they were talking, she told him that she knew about all the perversions that they were engaged in together. At that moment, when he had already thought that he was getting into, a mature woman with great breasts tells him that in gratitude for everything he did for her daughter, she would let him fuck herself as much as he wanted.