Mesu Kyoushi: Injoku no Kyoushitsu

Episodes:3

Summary: Toudou Miyuki and Sanada Eiji are teachers in the same school and
lovers. They had decided that they would preserve their chastity until
they are married. However, Miyuki is assaulted and loses her virginity
to Takuya, Eiji's step-brother. Furthermore, it doesn't stop there as
Takuya turns his attention on the other female teachers one after the
other.