Disclaimer: The author does not condone piracy. You must own a legal copy of Ninja Katsugeki: Tenchu San Portable (UMD or digital PSN backup) to apply this patch.
When FromSoftware (the developer) and Sega (the publisher) brought the game to PSP in 2009, they didn't just port it. They enhanced it. Ninja Katsugeki - Tenchu San Portable English Patch
The Catch: It was never localized for North America or Europe. The PSP library was shrinking by 2009, and Sega decided the translation cost wasn't worth it. For 14 years, the definitive portable version of Tenchu was a Japanese exclusive. Disclaimer: The author does not condone piracy
"To deliver the definitive Tenchu experience on portable hardware, with all the humor, horror, and stealth intact. No machine translations. No cut corners." The Catch: It was never localized for North
The PSP port includes a full remake of the first Tenchu: Stealth Assassins (PS1, 1998). The patch translates:
With the Ninja Katsugeki - Tenchu San Portable English Patch complete, the community is now turning its eyes to Tenchu San Portable’s sequel—Tenchu 4 / Shinobi Taizen. Furthermore, rumors suggest that the success of this patch has encouraged a small team to attempt a full texture remaster for the PPSSPP emulator (4K resolution, upscaled UI).
For now, though, if you have been waiting nearly two decades to play the ultimate version of Tenchu: Wrath of Heaven on your commute to work, your wait is over.