Harafure ~Soku Ochi Betabore na Haramase Onaho Sefure-tachi to Saru Mitai ni Yarimakuru Gakuen Harem Seikatsu~

A world where dick skills are placed above all else.
However, no one will look at your dick unless you have other skills...
While you were being bullied the kind gyal Kirari suddenly helped you, and you got hard!
She didn't seem bothered by it... in fact, she was super curious and you end up
having sex and instantly turning her into your loving sex-hole friend!
Kirari tells her friends about your dick and other girls flock from around the school
to have wild mating sex with you as you impregnate girls in your harem school life!

[From DLsite English]