Besides lowering the graphics settings in the launcher, there are additional settings in the config menu. Depending on your needs you can lower the number of mob NPC's and heroines loaded. Another major help is lowering the map loading limit, the draw distance will be extremely short, and beware of falling through the ground, but performance may improve greatly. Disabling the scanner is known to help FPS too, but that currently has a glitch so lowering it's range is the alternative