Shiina is the quiet accountant at his company, isolated from the rest of the department and seemingly easy to approach. What begins as a way to relieve workplace stress changes when he discovers her huge breasts, big ass, and extraordinary sensitivity after a long dry spell. She gushes and climaxes again and again, making him feel irresistible. Deciding she is too good to remain merely a discreet married fuck buddy, he sets out to shape her into the kind of mistress he wants.