Secretly fucking sister-in-law behind her brother's back

A movie by Minami Kojima, she became a secret lover with her brother-in-law after being raped by him. Minami has a fairly happy marriage with her husband. One day, her husband's younger brother came to live with his older brother while looking for a job. Seeing his beautiful sister-in-law made the younger brother infatuated day and night, and he accidentally witnessed his sister-in-law and his older brother making love, which intensified his desires. Therefore, one day when the older brother went out to work, he took the risk to see if he could have more.