Kingdom Hearts Union χ

Kingdom Hearts χ,[1] stylized as Kingdom Hearts χ[chi], is a Japanese role-playing browser game developed by Square Enix, BitGroove and Success, and published by Square Enix for web browsers as the eighth installment in the Kingdom Hearts series. Gameplay involves players navigating a customized avatar through Disney-inspired worlds fighting enemies, along with taking down bosses in multiplayer matches in competition with other teams. A version of the game for mobile devices called Kingdom Hearts Unchained χ, was released as the ninth installment of the series in Japan in September 2015, and worldwide in 2016. In April 2017, Unchained χ was rebranded as Kingdom Hearts Union χ[Cross].

Kingdom Hearts χ is a prequel to the Kingdom Hearts series as a whole, taking place centuries prior. It takes place before the Keyblade War, which established the organization of the Kingdom Hearts universe as of the original game. The player assumes the role of a Keyblade wielder who joins one of five factions led by Keyblade Masters fighting for control of the limited light existing in the world. Unchained χ/Union χ acts as a sequel, retelling part of the story of Kingdom Hearts χ before diverging and telling a new story set after its events. The game's plot is connected to Kingdom Hearts III, the next main entry in the series. The title refers to the χ-blade, a weapon central to the series' story arc.

The game was designed as a playing experience that newcomers to the series could come to. Its presentation was compared to that of a fairy tale, as depicting the usual style of the series would have been difficult on the platform. Both Tetsuya Nomura and Yoko Shimomura, veterans from the main series, returned as director and composer respectively. The game received favorable reception from critics. A companion film, Kingdom Hearts χ Back Cover, was released as part of Kingdom Hearts HD 2.8 Final Chapter Prologue in January 2017.