Onna hisho no namashitagi: Hagitoru (1991)

Identical twin sisters, the older sister has a fetish for black rubber underwear and is M. My sister has a fetish for white rubber underwear and is S. They looked so similar that it was impossible to tell them apart, but other than their love for different underwear, their tastes in sex were completely opposite. Her sister works as a secretary to the president of a certain company, but the president has no respect for his wife, who is the son-in-law of the company's founder and the founder's daughter. She vents her anger through intense and self-righteous sex with her sister, who is her secretary. Her younger sister is worried about her older sister, and one day, with her S-like ambitions, she approaches the company president, but...