再婚し嫁いできた千里。新しい家庭では義理の息子が出来たが、年の離れた初老の夫との再婚だったため、夫は夜のほうが淡白。逆に義理の息子とは比較的年齢も近く、お互いにドキドキし緊張しがちな間柄だった。夫が長期出張でいなくなり、昼下がりのある日、つい暇を持て余して自慰をしていたら、たまたま早く戻ってきた息子にその恥ずかしい行為の一部始終を見られてしまう。そして「黙っている代わりに」と、弱みに付け込まれ、息子の淫らな欲望に応じてしまう。その時から、身体を許した事がきっかけで息子との秘め事は続いていく・・・。Chisato has remarried and married into a new family. In her new home、 she has a son-in-law、 but because she remarried an older man、 her husband is more reserved at night. On the contrary、 she and her son-in-law are relatively close in age、 and they tend to be nervous and nervous of each other. One day、 when her husband was away on a long business trip and she had too much free time on her hands、 her son happened to come back early and saw the whole embarrassing act. He takes advantage of her weakness by saying、 "Instead of keeping quiet、" and gives in to her son's lewd desires. From that time、 the secret thing with the son continues by the thing which allowed the body....