The Erotic Paradise (Eden) in the Attic ~First Sex Lesson for My Cute Student~

The cram school, renowned for its headmaster Shiina's charming looks and meticulous teaching, had a secret attic room!
A month after joining the school, the beautiful Inori was invited to the attic room for the first time.
There, she received an unexpected confession from Shiina.
"Will you be my girlfriend starting today?"
"Y-yes... if Inori is good enough for you, I'd be happy."
Inori blushed and nodded happily.
At that age, she was more attracted to older men than boys her own age.
Inori was no exception; she had fallen in love with this man, Shiina.
...Little did she know he was a succubus disguised as a gentle, refreshing man.
Shiina placed his hand on Inori's shoulder and whispered in her ear as if sharing a secret.
"Hey, since we're finally alone together, how about we have a special lesson now?"
A secret special lesson takes place in the quiet attic room.

The time is the near future.
Due to the effects of a pandemic, the world’s male population has drastically decreased. With birth rates plummeting and the continued threat of human extinction, there is much clamor about the crisis—
Around this time, you move to Kawashima (交島), a single-town island floating in the southern seas off Seisui Prefecture, where your grandfather has an empty house. It is an isolated and desolate countryside town, but it is home to an academy designated by the country as an educational leader.
You are moved by meeting classmates of the same sex, something you’d never experienced before. You become accustomed to interacting with the unique girls and your self-sufficient life after school.
Then, during a class one day, the health teacher, Hirari-chan, announced abruptly without even a proper greeting:
 
“Starting today, you will all be having sex!”