Performance issues, potential workaround(s)...
Also note: for those suffering from really poor (constant -- not spiked or frozen for a moment scenarios, this will happen) frame rates when playing... Of course, lower graphics settings, for Nvidia cards kill Anisotropic settings, all off (from what I understand AMD cards don't have this as a modifiable setting)...
In game, only release girls as needed until you unlock the housing island. Travel to the housing island (you'll notice a 50%+ bump in frames), build a decent home and setup all the things you need (farm plots, chicken coup, playground, library, kitchen, bathroom/bathing facilities, bedrooms) then invite two of your girls to the housing island. Then unlock whatever girls aren't unlocked on the main island and train them up fast. Now alternate back and forth 1-2 days at a time and you will notice a 25%+ bump in frames as a constant, with common average frames riding higher than 60fps.
Note: if in the beginning with just the Merchant and first girl, if you aren't getting at least a common average of 25+ fps, this game will be unplayable for you. You either need a new graphics card, or you are bottlenecking at the processor, RAM, motherboard, or the Hard Disk. Use your resource monitor (on Windows there is a built in one in the Task Manager) to see what is being slammed the hardest. Also, I noticed that the game wants to pull a pretty constant 8-12GB of RAM with spiked that go above 16GB at times. If you have less than 8GB of RAM this will likely be unplayable, and under 12 you will likely freeze a lot randomly as the girls move about...
I am working on a mod to optimize the video settings and also to add additional girls to the game (for those without much issue running 4 girls, the merchant, and player in the same zone) I am thinking of using the housing island terminal as the location to add more girls. This way if you add in 4-5 on the housing island, you know you will still perform well. If you add in a 6th and it starts slamming the computer, you can send 1 to the Ruined Island. This way people can establish their own maximum and spread them between the two islands accordingly.