I'm guessing you're having the triad issue in chapter 5 where you have to outrun them.
Turn OFF frameskip, firstly, not needed for you.
When ingame, pause emulation>settings>System>"Change Emulated PSP's CPU Clock (unstable)" to 111mhz, or 222mhz, or, just fuck around with it a bit till you find something that works. It won't hurt to try. Lower will help more than higher for this application.
I'm hoping you're on a PPSSPP version newer than 2020, which would make sense if you don't have forcemax60fps, but possibility remains that you may be on one older than sept2021 when
hrydgard added Kurohyou 2 to the baked-in forcemax60fps system. (Or, says he did, lol)
I tested using the savestate found
here with the demo AND full game (translation included) on the most recent version of PPSSPP (1.17.1) and was able to get through without any issue at all using default settings. My emulation rig is similar enough to yours that it shouldn't be an issue, was mostly concerned if you were on a latitude or something. If clock speed adjustment doesn't work, there are two cheats in the second github link that increase movespeed (one for the demo, one for the full game, it works even on the patched iso), turn one on, speed past, turn it off, repeat when necessary.