Hidero Ohsawa

The first teacher Eikichi Onizuka meets at Musashino Public High School during training, Hidero Ohsawa has a reputation for sleeping with his female students and convinces Onizuka that teaching high school is the way to lose one's virginity. He states the prospect of having a beautiful, 16 year-old wife, even at the age of 40, is irresistible to the ears of the 22 year-old Onizuka. Upon learning that Nanako Mizuki has been staying over at Onizuka's apartment, with no action going on, Ohsawa insists that he forces himself on her, and videotape it to keep her quiet about it (ensuring that Onizuka's "merchandise" won't go to waste). However, Onizuka does not follow-up with Ohsawa's advice.

Ohsawa is not seen, after Onizuka finishes his training, but it is revealed that he was caught having an affair with a student, and left for another training session, away from Musashino High.

Source: Wikipedia