Private Netori Academy.
For some reason, many of the girls at this school have boyfriends.

The protagonist, Kashiwagi Dankonmaru, a creepy, nerdy, and over-the-top boy who attends the school.
Dankonmaru was always thought of as creepy by the girls, but in fact, he has a natural talent that everyone envies.
And that talent is that he's really good at sex!

When Dankonmaru realized that, he arrived at the truth:
"Maybe it's okay to force myself on them, as long as they're satisfied?"

And so, awakened to his own talent, Dankonmaru begins to seduce all the girls with boyfriends in school.

[From Gyutto]