The experience is currently a 7/10. If you have a Nintendo Switch emulator set up and you own a legal copy of the game, you can enjoy a superior 4K experience right now.
While the ShadPS4 emulator has made incredible strides (running Bloodborne at playable speeds), Catherine: Full Body is a different beast. The PS4 version relies on specific audio codecs that current PC emulators struggle to decode. Expect crackling audio, missing texture layers on the tower blocks, and save file corruption. Catherine Free Full Body Pc Emulator
Emulators themselves (Ryujinx, Yuzu, ShadPS4) are free, open-source software. That is legal. However, the that allow you to play Catherine: Full Body are copyrighted intellectual property of Sega and Atlus. The experience is currently a 7/10