Siakama

If this game is lagging, or any other games that were made in danmakufu, this one just seem to be the biggest offender, even if the GPU is not being used that much and you actually have a decent or better GPU that's from NVIDIA, it could be because you have the "Maximum Frame Rate" in your NVIDIA Control Panel turned on, turn it off and then try to run the game, it caused my game to run at 5FPS because I set max FPS to 60FPS, I have no idea why it does that, image below for some kind of direction, sorry that's in Portuguese, in English it's probably something like "3D Settings -> Manage 3D Settings", if that still doesn't work and your PC is decent, try restoring the standard settings, else, I don't know. If you have a GPU from another company, try doing something similar. Also, if your NVIDIA Control Panel doesn't open, open the "Task Manager" and go to "Services", search for "NVDisplay.ContainerLocalSystem", if the service is stopped, press the right mouse button on it and press start, if it already is running, try restarting it, else, I don't know how to fix it, googling about it might help.