Onna Kyoushi Yumi no Houkago / Hot for the teacher

Yumi is an incredibly beautiful dark-haired girl with big breasts - works as a teacher at a local academy. She is good at everything, both at work and in life. But a recent breakup with her boyfriend somewhat depressed her, and the perverted academy director took advantage of this. He seduced Yumi and made her a sex slave "which is typical for hentai, by the way". Soon she meets other sex slaves Keiko and Atsuko. With their help, Yumi will try to escape from slavery.