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In the full interview about Kingdom Hearts 2.5 HD Remix, Famitsu asked Nomura on a status update on the development of Kingdom Hearts III. In his answer, Nomura stated that development was proceeding as planned, however the team is no longer using the Luminous Engine and have switched to the Unreal Engine 4 for a variety of reasons. He says that because of this switch there have been having some graphical rendering issues but that Epic Games is working closely with the development team to resolve them. Famitsu Interview. Translation regarding the change to the Unreal Engine courtesy of duckroll at NeoGAF.
To coincide with the release of Kingdom Hearts 2.5 HD Remix in Japan, the Kingdom Hearts Memorial Ultimania also saw a release. This guide contains content pertaining to every single Kingdom Hearts game that has been made available in addition to some some exclusive interviews and messages. Included among this was a message from series creator, Tetsuya Nomura regarding Kingdom Hearts III. Thanks to sqex.info for the translation.