Party member

Party members (仲間キャラクター) are allies who fight alongside the protagonist, often with customisable behaviour, equipment, items, and abilities. They have their own HP and MP gauges, displayed above the protagonists'. Generally, a defeated party member is knocked out temporarily for a certain period of time, unless they are healed.

Cooperation characters (協力キャラクター) are similar allies who only appear during certain story sequences. A distinctive feature is their lack of health gauges, which makes them invincible.

There are also other allies who help during certain battles to provide some sort of support, often by opening up new attacks for the protagonist to use.

Kingdom Hearts
Party members have individual stats and can be equipped with items, accessories, and weapons. Party members have different base stats, abilities, and number of item and accessory slots. Each party member has their own weapon type and cannot equip weapons of any other type. They earn experience and level up independently to Sora and are rewarded with stat boosts, new abilities, more item slots, or more accessory slots when levelling up. While Donald and Goofy are permanent party members, many worlds provide a third ally. World-specific party members have limitations as each of them has only one weapon that they can equip and levelling up solely grants stat boosts.

Only two party members can be placed in the active party at a time. A menu to swap party member positions can be accessed at Save Points and whenever a party member joins or leaves the group. Experience is granted to party members, even if they are not in the active party or they are in another world.

In battle, pressing causes party members to attack the locked-on target. There are several enemies that are never targeted by party members, including the White Mushroom, Rare Truffle, and Black Ballade.

AI customization
From the "Customize" tab in the pause menu, a party member's AI can be altered to perform actions at different frequencies, which can create specialised fighting styles. There are a number of pre-made fighting styles to select: Offensive focuses on attack, Defensive concentrates on recovery and defense, Conservative preserves MP and items, and Balanced provides a mix between offense and defense. In addition, each party member has a unique Personal fighting style and with Manual, the player can create their own fighting style.

Frequencies can be set on a number of different actions and each party member has access to a particular set of actions. Each action can be set to one of three frequency levels, "Constantly", "Frequently", or "Occasionally", with the exception of the HP Items and MP Items actions which instead use "Immediately", "Frequently", and "Only in emergency".

Kingdom Hearts: Chain of Memories
In sync with the game's card-based system, party members are replaced with Friend cards, which temporarily call allies onto the battlefield to perform attacks.

Kingdom Hearts II
Party members have individual stats and can be equipped with items, armor, accessories, and weapons. Party members have different base stats, abilities, and number of item, armor, and accessory slots. They earn experience and level up independently to Sora, which reward them with stat boosts. Obtaining bonuses provide party members with further stat boosts, new abilities, and more item, armor, and accessory slots. Limits are new techniques that allow Sora to perform powerful attacks with a party member. While Donald and Goofy are permanent party members, many worlds provide a third ally. World-specific party members have limitations as each of them has only one weapon to equip and bonuses do not provide item, armor, and accessory slots.

Only two party members can be placed in the active party at a time but switching between party members is much smoother than in the original Kingdom Hearts. In the Command Menu, a "Party" command allows the player to swap out a party member on the fly, even if they are fallen. Support abilities, such as Auto Change and Auto Healing, can be equipped on party members to aid the process. Party members can also be swapped around from the "Party" tab in the pause menu. Experience is granted to party members, even if they are not in the active party or they are in another world.

AI customization
In the menu's "Customize" tab, the player can change their party members' settings. Each enabled action ability can be set to be used at a different frequency, ranging from "Free", "Well-Balanced", or "Rare". Like Sora, party members can enable Auto-Reload through a toggle for each item slot.

Also, each party member's behaviour can be set to a particular Battle Style:
 * Technic Attack: Party Members fight with their individual techniques.
 * Target Attack: Party Members concentrate attacks on Sora's target.
 * Huddle Attack: Party Members fight close to Sora.
 * Party Attack: Party Members will fight a target other than Sora's.
 * Sora Attack: While Sora attacks, Party Members will support him.
 * Relentless Attack: Party Members defeat their target before attacking another.

Kingdom Hearts 358/2 Days
Members of the Organization XIII are automatically assigned as party members on certain missions. Typically, only one party member accompanies Roxas on each mission, although Mission 56 begins with two party members and Roxas works alone for many other missions. In battle, party members physically attack enemies and cast magic. In multiplayer Mission Mode, other players are displayed as party members.

Kingdom Hearts Birth by Sleep
Party members only appear during certain events in the story, similar to cooperation characters from Kingdom Hearts II. Friendship Commands are most effective within a party, especially when playing multiplayer Mirage Arena. Enemies do not grant experience if it is defeated by a party member. Some commands, like Group Cure, support party members through restoration or buffs, while other commands, such as Trinity Limit, are attacks that deal extra damage with party members.

In some sequences, an ally must be escorted through an area of Unversed. A "Damage" gauge fills up when the ally takes damage, forcing "Game Over" when full.

In the company of a party member or escorted ally, Dimension Links are disabled and several Reaction Commands may be triggered.

Kingdom Hearts coded
Only two worlds feature party members in Kingdom Hearts coded, and they each use different gameplay systems.

In Olympus Coliseum's turn-based combat Labyrinth, party members perform exactly the same as Data-Sora, although "Game Over" only occurs if Data-Sora dies. Each party member has a different special attack and amount of health.

In Hollow Bastion I, Data-Sora cannot attack and instead issues instructions to his party members. In place of Attack, the Ask for Help command cycles the party members' focus between following Data-Sora, attacking enemies, and destroying Bug Blox. Deck commands are replaced with new commands that party members carry out; a deck command's type determines which party member executes the new command. Finish commands are disabled, except Spinner Ray which can be used when both party members have joined the party. If a party member's HP is reduced to 0, they can be revived by going to them and using Rescue.

Kingdom Hearts 3D: Dream Drop Distance
Spirit Dream Eaters act as Sora and Riku's party members and are synthesized out of Dream Pieces. They each have different stats, abilities, and Ability Link boards. The new Link System allows characters to perform powerful techniques with Spirits. Only three Spirits can be brought into the party at a time and only two fight alongside Sora or Riku. Spirit positions can be changed within the party by dragging their icons around on the touch screen. Experience is only awarded to those in the party. In the "Spirits" tab of the pause menu, Spirits can be placed in and out of the party. If a Spirit's HP reaches 0, it can be revived by using Rescue within 30 seconds; failure to do so results in the Spirit reverting back to a Dream Piece permanently. When selecting a New Game Plus, Spirits carry over with their stats.

In the opening battle against Ursula on the Destiny Islands, Riku acts as a cooperation member to Sora. Riku can attack with his Soul Eater and heal.