If MC was a harem protagonist this would be a major issue. At this point be like a stereotypical isekai character to survive.
This is one disease where everyone will be in trouble. The only way I can see someone surviving is if they are castrated (surgery/chemical) impotent or at an age/state where arousal would be impossible.
Considering it's by the creator of Gunjo Senki, I'm not surprised. I suppose it's the next step from students surviving murderous Sengoku era warlords.