Final Fantasy Type-0
"Final Fantasy Type-0" was originally titled "Final Fantasy Agito XIII", envisioned as a game for mobile devices. It was conceived in 2005 as part of "Fabula Nova Crystallis Final Fantasy", a subseries of "Final Fantasy" games linked by a common mythos. "Agito XIII" was the final original "Fabula Nova Crystallis" game to be created. The decision to make it a mobile game was based on the popularity of "". Hajime Tabata, who contributed to the "Fabula Nova Crystallis" mythos, was searching for a new project after finishing "Before Crisis" and became the game's director. "Before Crisis" producer Kosei Ito acted as producer before his move to Capcom prior to 2009. Beginning development in 2006, it was first announced at that year's Electronic Entertainment Expo (E3). It was said to offer on-the-go access to the "Fabula Nova Crystallis" universe, using gameplay functions exclusive to mobile phones of the time. The concept was to deliver a game for mobile platforms equivalent to a console game from the main "Final Fantasy" series, and to make it available in its entirety upon release rather than in episodic format.
Spiritual successor
One example of a spiritual sequel resulting from legal issues is "Dark Souls" by From Software, inspired by "Demon's Souls" by the same studio. The rights for "Demon's Souls", an exclusive title for the PlayStation 3, was held by Sony Computer Entertainment, preventing From Software from making a successor on other platforms, leading them to create a new property with similar gameplay mechanics for the Xbox 360 and other platforms. Another example is "Perfect Dark", developed by Rare as a spiritual sequel to their licensed title "GoldenEye 007". Rare had planned to develop a sequel to "GoldenEye" but lost the license as they were outbid by Electronic Arts. The developers still wanted to complete another spy-based title and developed "Perfect Dark" with a new story but with similar mechanics to "GoldenEye". 
All "Final Fantasy" games in the original series are spiritual successors of the original game rather than being sequels. The first proper story sequel was "Final Fantasy X-2".