Shiina Miyu no Chitai Sen'you Gakuen

Miyu Shiina—a girl whose body may succumb to pleasure, but whose heart will never break.
To make her completely his, Takumi Shiki devises a grand plan. Disguised as a student teacher, he infiltrates the school Miyu attends…!
Can Miyu endure the six-hour "lesson in humiliation and ecstasy" that awaits her?!
This is a hardcore erotic adventure, depicting Miyu as she’s overwhelmed by shame and pleasure within the school’s walls.

[Translated from dlsite]