World of Final Fantasy is primarily set in the world of Grymoire, a land populated by classic Final Fantasy characters and monsters from across the series, while being unconnected to any other series entry. The storyline focuses on twin siblings Lann and Reynn, who suffer from amnesia and hold the power in one of their arms to capture and wield Mirages, the monsters of Grymoire. Lann and Reynn travel to Grymoire to recover their memories, gradually mastering their powers and becoming involved in the conflicts consuming the world - these include fights between rival factions within the native Lilikins, and the impending threat of the Bahamutian Army.
Development started around the concept of a Final Fantasy title aimed at a wider and younger audience, focusing on a light tone and stylised graphics compared to the mainline entries. It was directed by Hiroki Chiba, who had worked as a scenario writer and event planner for the series and also wrote the scenario for World of Final Fantasy. The chibi character designs, which had been used for Pictlogica Final Fantasy, were created by Yasuhisa Izumisawa; the larger characters were designed by Tetsuya Nomura. The music was composed primarily by Masashi Hamauzu, who also included arranged versions of classic themes while aiming for the music to be lighter in tone.
First announced at the 2015 Electronic Entertainment Expo, World of Final Fantasy was intended as a celebratory title to commemorate the series' 30th anniversary. A worldwide release was planned from an early stage, with localization running parallel to the development and Japanese voice recording. In order to keep the characters true to their original appearances, the localization staff who first handled them were brought in to translate their dialogue.
World of Final Fantasy is a role-playing video game in which players take control of twin siblings Lann and Reynn as they navigate the world of Grymoire. In Grymoire, all the characters and monsters encountered by the player are rendered in a chibi-style. The exceptions are Lann and Reynn, who can shift at will between chibi form and their true forms. During their travels, Lann and Reynn befriend various monsters called Mirages that they can utilize both in battle and within the navigable environment: examples of this usage include riding larger Mirages as mounts or using them to navigate environmental puzzles. The game's battle system makes use of the Active Time Battle (ATB) system employed by multiple Final Fantasy games. In battle, players control a party of Mirages which can be stacked upon each other to grant various boons in battle while decreasing the number of turns that can be taken. The types of Mirages used affect the party's available skills and abilities in battle. Mirages are befriended in battle after they have been sufficiently weakened, and once in the party can be freely named. In addition to standard Mirages are special Mirages that can be temporarily summoned into battle using Action Points (AP): the Mirage remains in battle, replacing the main party, until the summoner's AP is depleted.
In the beginning of World of Final Fantasy, the story begins in a town called Nine Wood Hills, and they travel through a portal to the world of Grymoire. Grymoire is a land where multiple locations from earlier Final Fantasy titles, such as Cornelia (Final Fantasy) and Saronia (Final Fantasy III), fuse together and where multiple climates exist side-by-side. The main inhabitants of Grymoire are the chibi-like Lilikins, while its monsters are called Mirages. The protagonists and others like them are referred to as "Jiants".