Play as Cody, the new owner of a Robopon Dispatching Company after his grandpa retires. You start with one Robopon named Sunny and must travel across Porombo Island to collect more Robopons and battle against other collectors known as the "Legend 7". Beating a Legend 7 member earns you their rank, and upgrading your Robopon is key to success.
Gameplay involves collecting Robopons, battling against opponents, and upgrading your creatures to improve their strength. The battles are turn-based, where you tell your Robopon to issue attacks or go on the defensive. You can also heal your Robopon in mid-battle with spells purchased from town shops or found in between towns. Defeated Robopons sometimes drop add-on items that get claimed by the winner.
Robopon Sun Version , released for the GameBoy Color in 2000, features a total of 153 different kinds of Robopons. Completing all of them requires trading between versions using an infrared sensor, adding a unique twist to the game. The game asks for your birth date at the start to select the first Robopon you'll begin with.