The MC is an idiot. He may as just serve his girl up himself at this point.
Like man, you know your friend is plowing everything in his path and you tell him your girl is untouched. He clearly wants your girl's gams and is able to get with women that are considered hard to get.
Stepping outside of eroge logic, if MC's friend is just SA-ing these women then it's a matter of getting them to come forward, but if he slinging dick that good that they won't come forward then that's on them. MC doesn't have to save every girl around him, just focus on his own. Neglecting your girl is how you lose her dumbass.