It has been several months since her husband's younger brother, Kazuo, came to stay with the Sawamura family while he was preparing for his entrance exams. In order to encourage Kazuo, who feels ashamed about having failed the exam twice, Reiko verbally promises him a reward if he does well on the mock exams. Kazuo, who secretly adores her, says, "Then I want to kiss you, sister-in-law!" As a result, Reiko gets a great score and is given a reward. However, she is aroused by the intense and rough kiss that her husband does not have, and she cannot get the passionate kiss out of her head...