Can you beat the game without prostitution/sharing any girl? Looking for a challenge.
That really depends on your definitions.
Assuming
no sharing = only 1 partner.
no prostitution = no brothel
Assuming unmodded:
Neutral
& Ruin ending ? Probably. You will be buying many girls because you will likely not be able to reproduce them.
Harem *
& Ruin* ending ? No. You need Sena & Lena favor, which requires the ranking up of the brothel, which would be "prostitution"
Assuming Complex Breeding:
Neutral
& Ruin ending ? Probably. Due to girls being able to create female offspring with monsters under circumstances, you won't need as much buying.
Harem
*& Ruin* ending ? Again, no. Same reasons. There is no job in CB that could increase favor with Sena & Lena as a bypass. (No job that increases favor with Amelia, but she shouldn't be a problem regardless)
If brothel usage is fine as long as partners doesn't go beyond 1...
That would be a lot of micromanagement.
(unless non penetrative is fine, tho the game DOES count it)
EDIT: One correction. Since brainwashing requires full favor, the Ruin ending isn't doable in this challenge either.