This is a used game. It has been tested and works fine.
Game Boy and Game Boy Color games are not region locked. So you will not need a Japanese system to play this.
This cart contains 20 games, which you can see listed in the photos. These are all the Japanese versions of the games as far as I can tell. The Pokemon games are all definitely in Japanese.
I was able to easily put a fresh new battery into the cart. I tested it and the save functions work. But the cart can only hold one game save at a time. So you sadly can't juggle between the Pokemon games really.
****Please closely inspect photos before making a purchase. Thanks!****