Secretly fucking her 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 quite happy marriage with her husband. One day her husband's younger brother came to live with his older brother while looking for a job. Looking at his beautiful sister-in-law made his brother-in-law passionate day and night, and accidentally seeing his sister-in-law and brother having sex made his lustful blood grow more and more desirous. So, when his brother went out to work one day, he stayed at work to see if he could eat a lot.