Mission Mode

Mission Mode is a gameplay mode is available exclusively in Kingdom Hearts 358/2 Days. Through Mission Mode, two to four players can compete in missions across the worlds, and it can also be played solo. Mission Mode uses the Nintendo DS's wireless capabilities to compete with other players, but all players must have a copy of Kingdom Hearts 358/2 Days. Items collected and character growth in Mission Mode carry back to the save file the player selects at the start. Guest Play can also be selected, where upon the player is given preset items instead of those obtained in Story Mode.

Solo play was a more developed feature in the English releases of the game. In the original Japanese version, Mission Crowns -prizes from completing missions- are only awarded in multiplayer mode, whereas in the English version, they can be obtained in solo play. Also, the selection between solo and multiplayer was made more clear cut in the English release. Unlike the Japanese version, selecting "Mission Mode" in the English version offers a choice between solo and multiplayer on the main menu. The Japanese version instead brings the player straight to the Wi-Fi group menu, but the player can continue alone without other players.

At first, the player only has access to thirteen characters, all members of Organization XIII. However, as the player progresses through Story Mode, an additional six secret characters can be unlocked.

Pre-mission setup
Right from when a player accesses the main menu, they have the option of playing either the main game, Story Mode, or the multi-playing Mission Mode. After the player selects the "Mission Mode" option, they are taken to the Character Selection Screen. They are given a chance to view the stats of the character they choose, which are each represented graphically on a scale from 1-10, just before being taken to the Menu Screen. The player only has access to Organization XIII to begin with, later gaining access to new characters as they play through Story Mode.

At the Panel Customization Screen, players have the ability to select weapons, items, spells, and abilities that are to be used during competitive gameplay. It should be noted that players will also have access to items gained during Story Mode. It is then that each player is taken to the Mission Select Screen, the last screen to appear before gameplay begins.

At this last screen players select a world and a mission they would like to play from Story Mode that took place in that world. It should be noted that missions are made playable once their respective Unity Badge has been collected in Story Mode.

Gameplay
During actual gameplay, players work toward the same goals that Roxas would in Story Mode, collecting Mission Points along the way. Players can attack each other, stealing the targeted players' Mission Points as a result. While the Mission Mode is mainly a way to battle enemies with friends in an allied setting, its true intention is competition due to its friendly-fire format. Just as in Story Mode, a mission ends when the Mission Gauge is filled to the first, or sometimes only, marker. However, in Mission Mode, extra Mission Points can be gained by getting to the RTC in a certain amount of time.

At the end of a mission, the results of gameplay are displayed. The characters selected for play appear in the thrones of Where Nothing Gathers, the thrones' height determined by the number of Mission Points. Places are awarded as first, second, and third, each displayed by a gold, silver, or bronze crown respectively.

Mission Crowns are earned after completing missions. They can be redeemed at the Moogle Shop for various rewards.

Chatting
An especially new feature in Mission Mode is the ability to chat with other players. During a mission, players can message each other via stylus or in-game keypad. Various colors of text can be used, adding to the fun of this feature. From saying hello to requesting help tackling a boss while a friend is busy with another target, messages are displayed on the Nintendo DS's bottom screen along with Mission Objectives.

Enemy differences
In general, the Heartless and Nobodies fought in Story Mode will be in their respective places in Mission Mode, though some enemies have been removed when not integral to a mission, such as the Jumbo Cannon in Mission 73: Defeat Heartless in the Games, or Xigbar in Mission 61: Vanquish the Heartless Threat. Furthermore, enemies generally drop items much less frequently in Mission Mode. While not an actual change in game mechanics, the Saïx and Riku bosses were replaced with shadowy Anti-Saïx and Anti-Riku bosses, to prevent confusion between the bosses and the playable Saïx and Riku. Also, the enemies in Mission Mode are now three to four times stronger than they are in Story Mode.

Victory positions
These poses are used whenever a character is victorious in the Games at the Olympus Coliseum.
 * Xemnas: Xemnas simulates his movements during battle before standing triumphant.
 * Xigbar: Xigbar crosses his Arrowguns before going into his battle stance.
 * Xaldin: Xaldin twirls two of his Lances around before crossing them behind his back in an "X".
 * Vexen: Vexen slashes the air with his shield before going into his battle stance.
 * Lexaeus: Lexaeus raises his Axe Sword high above his head before going into his battle stance.
 * Zexion: Zexion reads his Lexicon momentarily before closing it and wiping his brow.
 * Saïx: Saïx spins his Claymore before holding it diagonally in front of him.
 * Axel: Axel throws one Chakram into the air, spins and catches it, and then goes into the battle stance he used in Kingdom Hearts: Chain of Memories.
 * Demyx: Demyx strums his Sitar before striking a victorious pose.
 * Luxord: Luxord spins his Cards around him telekinetically before going into his battle stance.
 * Marluxia: Marluxia twirls his Scythe above his head before holding it behind his back with a reverse wield.
 * Larxene: Larxene hops twice before spinning and striking a triumphant pose.
 * Roxas: Roxas utilizes a pose similar to that of Sora in Kingdom Hearts, slashing the air twice before turning around and holding the Keyblade over his shoulder (When Dual-Wielding, Roxas spins the Oathkeeper and Oblivion before striking a triumphant pose, similar to his movements during battle when he's fought in Kingdom Hearts II Final Mix).
 * Xion: Xion spins the Keyblade and holds it to the side while brushing her hair off her face.
 * Riku: Riku twirls the Keyblade from left to right, then placing it at his side while looking down.
 * Donald: Donald hops and spins around twice before holding his Staff high above his head.
 * Goofy: Goofy jumps up and down in a manner similar to that in Kingdom Hearts, this time spinning every so often.
 * The King: Mickey simulates his movements during battle before raising his Keyblade high above his head in victory.
 * Sora: Sora slashes the air from left to right with his Keyblade before raising it high above his head and holding it over his shoulder.

Trivia

 * Because of his unique gameplay mechanics, Xigbar is Tetsuya Nomura's favorite character to play as.
 * The field theme from the Cavern of Remembrance was reused as the music that plays in the Mission Mode menu.