Kingdom Hearts Union χ

Kingdom Hearts Union χ[Cross], previously named Kingdom Hearts Unchained χ (キングダムハーツ アンチェインドキー), is a Kingdom Hearts game exclusive to the iOS and Android smartphone platforms. It features plot and gameplay elements from the Japan-exclusive web browser game Kingdom Hearts χ, and it is free to play but contains in-app purchases. It is the first Kingdom Hearts game to be released on smartphone platforms.

Kingdom Hearts Unchained χ was first announced on May 12, 2015. During Square Enix's E3 Conference on June 16, 2015, a trailer for the game was released showcasing gameplay. Kingdom Hearts Unchained χ was released in Japan on September 3, 2015 and in North America on April 7, 2016.

In April 2017, the game was rebranded with the Kingdom Hearts Union χ[Cross] content update, featuring multiplayer and a theater mode.

Development
While there were rumors of a localization for the web-browser based Kingdom Hearts χ, the smartphone game wasn't publicly referenced until April 14, 2015, in an interview with Tetsuya Nomura. The game was officially revealed on May 12, 2015, with the official title revealed in Famitsu magazine the following day.

On December 7, 2015, Version 1.1.0 was released. It raised the maximum level of Keyblades, added Adamantite Ore and matching quests, added Upright and Reversed Keyblade slot bonuses, and Special Attack Bonus.

On March 31, 2016, Version 1.2.0 was released. It raised the maximum Player level to 300.

On April 7, 2016, Kingdom Hearts Unchained χ was released in North America, starting at version number 1.0.0.

On August 4, 2016, Version 1.3.1 was released for the Japanese version. For the English version, it was called Version 1.1.2, and released on September 1, 2016. It added a Perks system for Avatar Parts, a daily Lux Boost function, and the ability to set up to three decks per Keyblade.

On November 2, 2016, Version 1.4.0 was released for the Japanese version. For the English version, it was called Version 1.2.1, and released on November 10, 2016. It added the Nova system.

On March 23, 2017, Version 2.0.0 was released for the Japanese version. For the English version, the update was released on April 6, 2017. It renamed the game to Kingdom Hearts Union χ, and added Union Cross multiplayer mode, Theater Mode, Medal Traits, Tutorial Quests, raised the cap for buffs and debuffs to 7, and the cost cap for Medals to 20.

On July 13, 2017, Version 2.2.0 was released for the Japanese version. For the English version, the update was released on July 20, 2017. It added completion percentage and icons to the Quest screen, MVP rewards for Union Cross, and a Perk filter feature for Avatar Parts.

On September 21, 2017, Version 2.3.1 was released for the Japanese version. For the English version, the update was released on September 28, 2017. It added the Pet System, increased the amount of jewels obtained as login bonus, made adjustments to several Story Quests, and changed the special attacks of all 4★ and lower Medals to match the 5★ version.

On November 2, 2017, Version 2.4.0 was released for the Japanese version. For the English version, the update was released on November 8, 2017. It added Booster items, the Mission feature, and added Auto battle to quests.

On January 18, 2018, Version 2.5.0 was released for the Japanese version. For the English version, the update was released on February 1, 2018. It added a low resolution option, and the option to display draw odds for Medal deals.

On March 23, 2018, Version 2.6.0 was released for the Japanese version. For the English version, the update was released on March 25, 2018. It added PvP Mode, 7★ Medals, Keyblade subslots, an optimize button for Keyblades, allowed players to skip certain Story Quests, and reduced the required materials for upgrading Keyblades, while removing some materials and matching special quests.

For a full list of updates and changes, visit the page on the Kingdom Hearts Unchained χ Wiki.

Story
After being saved by Ephemer and Skuld following the conclusion of the Keyblade War, Player is brought to another realm, where the Dandelions have assembled as per Ava's instructions. Upon entering this new realm, however, everyone loses all their memories of their previous world, with the exception of the five wielders chosen to become the new Union leaders.

Following Ava's orders, Ephemer ventures to the the Keyblade Graveyard as one of the new Union Leaders. Soon, Ephemer is joined by Skuld, the second of the new Union Leaders, much to his surprise. When Skuld questions the whereabouts of other three Union Leaders, Ephemer admitted that, before Skuld showed up, he had his doubts about becoming a Union leader. Ventus, the third Union Leader, arrives and Ephemer and Skuld welcome him. While waiting for the fourth Union leader to appear, Ephemer and Skuld bond with Ventus, who is bewildered as to why he was chosen to become one of the new Union leaders. He admits that he is a little jealous of Ephemer and Skuld's friendship, though they assure him that they consider him a friend as well. Amused by the concept of friends, the fourth Union Leader appears and introduces himself as Brain. When Ephemer confirms that Brain is not the last to arrive as he had anticipated, Brain asks if Ephemer is meant to be their leader. Ephemer denies this, feeling as though they should wait until all of them are together to decide who leads. Brain then asks if the rules Ava provided are meant to be absolute, as he has issue with the concept of lying to the Dandelions, something which Ventus relates to. Thinking about the pain that Player had endured because of the Keyblade War, Ephemer firmly states that they are to follow the rules and that the truth about the previous world must remain a secret so that no one has to remember the tragedy of the Keyblade War. Brain, Ven, and Skuld all accept this, stating that they all believe in Ephemer. Together, the four new Union Leaders await the arrival of their final comrade.

Player resumes his missions, initially reliving through the events leading up to the Keyblade War, and later making use of the newly created Union Cross, joining a party of fellow Dandelions and traveling to new worlds. Soon, Player has a nightmare in which he sees himself collapsed after the events of the Keyblade War. Furthermore, they relive their battle with Aced from just before the fated battle. Upon their defeat at Aced's hand, Player is jolted awake and Chirithy, concerned of the frequency of Player's nightmares, advises them to rest. As Player accepts this and warily returns to sleep, Chirithy bids them goodnight and continues to watch over them.

Prior to the Keyblade War, Strelitzia, another member of the Dandelions, takes note of Player as he waits for Ephemer in the Fountain Square, taking a keen interest in them. After witnessing Player's battle with Aced, Strelitzia is approached by Ava and asked to be one of the new Union leaders following the events of the Keyblade War. Concerned about those who will be left behind during the Keyblade War, Strelitzia remembers that Player is not a Dandelion, and insists that she has to warn Player of the danger that is to come. The next day, while searching for Player in an abandoned house, the two of them are attacked by an unseen assailant, who steals Strelitzia's rule book before leaving. Streltzia holds her Chirithy in her arms, sad that she did not get the chance to see Player, before both she and her Chirithy fade away.

Ephemer, Skuld, Ventus, and Brain grow concerned when the fifth Union leader does not show up and begin searching the Keyblade Graveyard. Soon, Lauriam approaches, apologizing for being so late, as he had been searching for something.

Together at last, the five enter the Foreteller's Chamber in Daybreak Town, where Brain looks through a copy of the Book of Prophecies that he finds. Ultimately, they decide to keep the Unions united under a Union Cross for the time being, while also keeping the absence of the Foretellers a secret. Brain then decides that in order to celebrate, they should make creating new Spirits their first task, sending Ephemer, Skuld, and Ventus to collect the supplies while he and Lauriam prepare to synthesize the materials.

Changes from Kingdom Hearts χ

 * have been replaced with s.
 * Players are able to switch genders and Unions at any time.
 * Overworlds have been replaced with the Quest system.
 * Action Points have been overhauled; they now function as a stamina system that enable the player to enter Quests and start Raids.
 * BP has been removed.
 * Lux and EXP have been consolidated.
 * New Heartless have been added.
 * New Keyblades have been added:
 * Stroke of Midnight
 * Fairy Stars
 * Sleeping Lion
 * Counterpoint
 * Fenrir
 * Darkgnaw
 * Missing Ache
 * Diamond Dust
 * New Worlds have been added:
 * Castle of Dreams
 * Enchanted Dominion