Four Play (1998)

Noriko Yoshifuku, supposedly flu-stricken, hasn't attended "college" since the start of sophomore year. When two of her classmates, Satoshi Akiyama and Junichi Ieda, are sent to bring her homework, the two young men discover that Yoshifuku does not have the flu at all. Instead, Yoshifuku can't stop thinking about (and acting upon) dirty thoughts and so she, Akiyama and Ieda act out their sexual fantasies while encountering obstacles along the way. The series's themes, developed in widely varying degrees, include wish fulfillment, bisexuality, incest, the ways in which sexuality can affect day-to-day life, and friendship.