The issues stem from the fact that the game uses DirectX 11 [en.wikipedia.org] as the rendering API, which is pretty old and does not take full advantage of the computing power of modern systems. However, we can remediate this by forcing the game to use the more modern Vulkan (DXVK) [en.wikipedia.org] API instead.

The process is pretty simple and involves dragging & dropping the DXVK library files to the game's directory. Below is a step-by-step guide on how to do so:

1. Download the latest version of DXVK files from dotsuijin's GitHub page[github.com]
   
   
2. The downloaded file will be in an archive (.gz) format. Use 7zip[www.7-zip.org] to access the archive
   
   
3. Since P5R is a 64 bit application, you will need to open the x64 folder and grab the files from there
   
   
4. Open the P5R's root folder by right-clicking on the game in your Steam library and selecting "Browse local files"
   
   
5. As we need to replace the game's DirectX 11 API, copy/drag only the following files and paste them into the game's directory where the game's P5R.exe file is located: d3d11.dll & dxgi.dll
   
   
6. Very important to avoid visual glitches in game - open up a text editor of your choice (Notepad, Notepad++ etc.) and paste the following in it: dxvk.enableAsync = true
   
   
7. Save the file as dxvk.conf in the game's directory, the same place where you pasted the d3d11.dll & dxgi.dll files. Whilst saving make sure to select the file type as "All files", otherwise this will be saved as a regular text file and will not be read by DXVK.

If you followed all these steps correctly you can launch the game and measure your FPS. Of course the gains will differ from system to system but in general you should notice an improvement, especially in crowded areas like Kichijoji and Shibuya/Central Square.

To put it simply - better utilisation of your computer's CPU and GPU computing capabilities. Below is a quote from Wikipedia [en.wikipedia.org] which explains this:

Originally posted by Wikipedia: Vulkan:

Vulkan is intended to offer higher performance and more efficient CPU and GPU usage compared to the older OpenGL and Direct3D 11 APIs. It does so by providing a considerably lower-level API for the application than the older APIs, that more closely resembles how modern GPUs work.

Vulkan is comparable to Apple's Metal API and Microsoft's Direct3D 12. In addition to its lower CPU usage, Vulkan is designed to allow developers to better distribute work among multiple CPU cores.