Is it possible to play Azel - PD RPG on a US SS with AR4M+?

I’ve recently imported the (cheaper) japanese version of Panzer Dragoon Saga, but it doesn’t start with the Action Replay 4M+ because the game is cartridge-protected.

Anyone who know any boot codes for Azel - Panzer Dragoon RPG? I’ve found a boot code for the european version, but they don’t work with the japanese game.

I’ve also read that an ST-key will work, so if there aren’t any boot codes I guess I’ll have to buy one, (or trade my US saturn for a japanese one)

An ST-Key is your best bet. Sadly, PD Saga is one of the few games that is incompatible with certain Action Replay carts (like the 4 in 1). Don’t worry though, an ST-Key is quite cheap AFAIK.