18+ Kyokon de Namahame Ou ni Nareru Gakuen

It's every teenage boy's dream! The entire school is a harem of horny girls who'll happily take a jizzload!

The instant they pulled down his pants, the world changed.
The protagonist was being bullied at the student council meeting when suddenly -- flash!
His exposed penis transfixed all the girls. He had his choice of any girl, but focused on
three in particular: the class president, the fencing club girl, and his angelic kohai (junior).

Part revenge tale, part sex spree, The School of Hard C*cks boasts sex anytime anywhere, in a variety of outfits!

(Source: dlsite)