Tômei Ningen: Gokuhi Waisetsu (1989)

Inventor Shinpei suddenly got a prescription for a rejuvenating elixir. However, the virgin joy juice necessary for the manufacturing method could not be obtained and it got stuck. Shinpei, who snooped on the affair of Keisuke Hanaya and Haruko, a female college student, became a transparent human when Haruko prepared it using paper wiped with love juice and drank the secret medicine that was made.