Mobile Suit Gundam SEED: Tomo to Kimi to Koko de is a strategy video game that was released on the Game Boy Advance console in 2004 by Bandai, the game was developed by Bandai. The game is based on the anime series, Mobile Suit Gundam SEED.
The gameplay of Tomo to Kimi to Koko de is split into two portions: "adventure mode" and "battle adventure mode". In "adventure mode", the player moves around the Archangel and interacts with the other crew members, which can lead to various side stories, some of which can lead to changes to the plot, unlock new artwork in the gallery, or unlock support units.

In "battle adventure mode", the player chooses their striker pack (only available with Strike) and support unit before entering a top-down map with the player mobile suit in the middle. A radar on the bottom right shows nearby enemy locations, and the status bar in the top left shows the player's health and energy. Pressing A sends out a cursor, which behaves differently depending on the weapon (ranged cursors shoot out across the screen, melee cursors remain close to the mobile suit), after locking onto one or more enemies, pressing B confirms the attack, after which a brief cutscene plays showing whether or not the attack connects, and how much damage it deals if it does. The reverse also happens if the player is attacked by an enemy. If the support unit is nearby when the attack takes place, it will perform a support attack on the enemy.

Attacking and receiving physical damage drains energy, and once the energy reaches zero, the player will suffer a Phase Shift Down, being unable to attack and receiving extra damage from attacks. Due to their nuclear reactors, the Freedom and the Justice slowly regenerate energy overtime, and will not suffer Phase Shift Down even after exhausting their energy supplies.

During most battles, the Archangel can be attacked by the enemy, and its health reaching zero results in a game over, requiring the player to protect it. The player can return to the Archangel to replenish energy or switch to a different Striker Pack, however, each Striker Pack can only be used once during each battle, and the player cannot sortie until the energy is fully replenished, leaving the Archangel vulnerable during this time. The player can also give limited orders to the support unit, asking it to either support the player, defend the Archangel, or return to ship for resupply.