Kangofu nikki: Waisetsu na karute (1980)

Ryoko is suffering from sleep deprivation due to her daily intimate encounters with her fiancé, Hirata. One day, she jumps into a taxi just before being late and meets the driver, Akira. Meanwhile, at the hospital, the director is plotting to marry his daughter, Yuka, to Hirata. After much deliberation, Hirata chooses Ryoko, but an enraged Yuka slips an aphrodisiac into Ryoko's drink...