Sigh (1973)

One day, Yumiko, an office worker, is called in by the managing director. Having been holding in her urge to urinate, she is ordered by the managing director to relieve herself in front of him, and embarrassed, she urinates into a vase. Later, when section chief Suzuki invites Yumiko on a drive, he takes her virginity that same day, awakening her to the pleasures of sex.