Those carts damage the Saturn's cart slot? That is news to me. However, since the only thing I'd be using the cart slot would be my Action Replay 4-1, it doesn't really matter really.
In Japanese, the game is hard to follow.... unless you read a script/translation or watch the english scenes online. If you really must follow the story in english, then get US (get ready pay a arm/leg to do so, lol).
I'm glad that the game lets you save first before switching discs. Otherwise that would be a probably suck. That sucks that Tengai Makyou IV doesn't let you save before hand before switching discs. I really wanted to check this one out.