Hello everyone.

I am looking for a gameboy/gameboy color game I played long ago, as a kid. However I do not remember the name, just a little of the gameplay. It goes like this:

You start in your own dungeon, which has three rooms (each with a key in it), and can place creatures in these rooms. You can also travel to opponents' dungeons.

The version of the game I played was also in japanesse.

Does anyone know the game?