Wakai Tsubomi ~Sensei...Watashi Mou Sensei ga Inai to...~

Ken'ichi Ono, a newly hired teacher at the school,
ends up having sex one afternoon with a student, Yukari Saitou.

Yukari, who has issues at home, becomes intensely attached to Ken'ichi after their first sexual encounter.
She stops resisting him entirely, no matter what he does.
And so, Ken'ichi’s training of Yukari begins.

Some time later, another student, Misa Yoshida, catches Ken'ichi in the act of “training” Yukari.
Misa tries to blackmail Ken'ichi, but he turns the tables and decides to train her too…

[Translated from the official website]