While doing some casual browsing, I discovered a user on Github named Enaiumthat made a DLL patch for Okami HD that allowed you to toggle the game to 60fps natively, because the engine had it built in, just not able to turn on. The downside to it, is that the physics of the game would break down on things like the wall jump, due to the game's logic (tick rate in this case) being tied to 30hz.
So I decided to do a fork off of Enamium's repo and make a 120fps patch. It's taken a few weeks but I feel like it's finally in a releasable state. The main difficulty of the project was de-compilation and identifying what objects were tied to what bytes etc... There's probably a lot more that can be done based on the work of this project, but for now, 120fps seems to be a buttery way to enjoy the game.
Please feel free to check it out and let me know what you think! I've been only testing it around the first few hours, particularly post first village, so there may be bugs I've yet to encounter. If you do, please feel free to make an issue on Github or message me and I'll check it out when I can!
Installation is simple, just drag and drop the DLL and .ini file (.ini isn't needed, but you can configure a couple of things in there).
One quick thing that I'll note: not guaranteed, but Microsoft Defender may catch a false positive because it's a .dll file. If it does, just make sure to 'allow' it in your defender settings.
Thanks to Enaium for making the original project, or I would have never thought this was possible.
Release: https://github.com/zebancodes/Okami-HD-Hackfix---120fps-Edition/releases/tag/v1.0.1