A few weeks ago, Tetsuya Nomura, director of the Kingdom Hearts series, said that Square Enix planned to announce a mobile game for the series later this year. The game, titled Kingdom Hearts: Unchained Key, has now been revealed as a free-to-play mobile adaptation of Kingdom Hearts χ [chi], and it will be making its way to iOS and Android later this year in Japan.
For those unfamiliar with the title, Kingdom Hearts χ [chi] is a free-to-play web browser game with a story that predates every other title in the series but is said to lead into the highly anticipated Kingdom Hearts III. The game centers around a combat system in which the player uses cards to battle. The game can be played alone or cooperatively with friends. As of now, Kingdom Hearts χ [chi] has only been released in Japan. Whether or not Kingdom Hearts: Unchained Key will be localized is yet to be announced.