Do As ~Oshishou no Iinari~

The protagonist grew up in a ninja village, thinking "There's no such thing as a ninja in this day and age." One day, he is selected to train Kaede, who is not making much progress in her training. He's usually annoyed by Kaede's fondness for him, but after seeing how much her body has developed recently, he's not entirely unhappy with the situation. He decides to teach her the art of lovemaking, under the guise of combat training. During escape training, he ties her up with a rope and starts playing with her! During combat training, he focuses on women's weak spots! And then...