I see lots of ROM hacks online where people have painstakingly translated games from different countries into English, sometimes using the help of language professionals to make sure all of the jokes and nuances of the speech have been carried over properly.
This translation PCB from Delta Island, however, allows you to play your actual games without damaging the hardware inside. It's a fully reversible solution should you decide that you want the original Japanese cart back, but once installed, you can choose to either translate the text to French or English depending on which PCB you choose.

The PCB is designed for SNES/Super Famicom games and can be installed with just a few connections. As you can see in this instance, this PCB is for Chrono Trigger and comes with 64 mb of flash memory to give you that extra oomph for completing optimised translations., plus a small switch lets you move from the original to translated versions with ease. There's also an option to keep the PCB updated with a PROG mode too.

Backups are fully compatible, and the design of the PCB means that you won't compromise your original cart in anyway whatsoever. Currently there's only Chrono Trigger available to order for a price of €24.90, though Delta Island are currently working on a translation PCB for Mother 2: Earthbound, so keep your eyes peeled for that dropping soon.