Because The Yakyuken Special was an eroge (erotic game), it was never localized for North America or Europe. In fact, due to Sony's strict content guidelines at the time—which eventually forced adult games off the PlayStation entirely and onto platforms like the PC-98 and Sega Saturn—the game is a relic of a brief, wild west period in the PSX's early life.
If you're looking to dive deeper into this game, I can help you with: Setting up for the best visuals Finding a list of other rare Japanese PS1 imports Troubleshooting BIOS or region-lock issues Yakyuken Special Psx Iso