...I don't get it. What's the point of this manga? This isn't NTR because his friend isn't going out or in love with any of these women, the girls are all manipulative or have hidden intentions, the MC actually likes his friend and wants to protect him so the general demographic of this sorta stuff who likes someone being cucked ain't getting any fuel.
At the same time, this has no power fantasy other than, well, sex, unless the author breaks the estabilished RPG superiority of the friend, which removes the biggest motivation for the MC to fuck, as the manipulative girls would be going for him instead, so generic isekai readers will also not really enjoy this, right?
At this point... why not just go read hentai? Or like, Parellel Paradise at least.