Tsukamattara Soku, Gyaku Rape Gakuen ~Shi ni Monogurui de Ore o Okashi ni Kuru Onna-tachi~

Kou Kisaka is the only guy in the entire school and he gets assalted from all sides by a legion of insane girls.
If he can just survive 3 more days, he'll be able to transfer out of school.
Until then he's constantly on the brink of slavery: if any girl gets him then his sperm will be squeezed to the last drop and that will be the end of his freedom...

[Edited from DLsite English]