There is no "free full body PC emulator" that offers a seamless experience. Most YouTube videos claiming otherwise are either fakes, malware-infected, or running the original Catherine (not Full Body) on RPCS3 (PS3 emulator).
However, for the average user searching for "free" files on Google: Catherine Free Full Body Pc Emulator
It looks like you're asking for a review of something called There is no "free full body PC emulator"