Ys: Memories of Celceta is not the first Ys game to take place in Celceta. In fact, a total of three other games have chronicled Adol’s adventures in the Great Forest of Celceta, each developed by a different third-party company, and each independently titled "Ys IV."
The development of Ys IV began when Hudson, responsible for porting Ys I & II and Ys III to the PC Engine (TurboGrafx-16), proposed the creation of a sequel to the company behind the series, Nihon Falcom. Busy developing another PC Engine title at the time, "The Legend of Xanadu," Falcom initially declined, but eventually accepted when Hudson suggested that Falcom simply create the base storyline for the game, while Hudson would develop the game themselves. As a result, Falcom’s involvement with this and other versions of Ys IV was limited solely to the original story and music.
While Hudson was busy creating their interpretation of Ys IV, another company known as Tonkinhouse (who had previously ported Ys III to the Super Famicom) began work separately on their own version of the game. Initially intended to be released on the Super Famicom (SNES) and Sega Mega Drive (Genesis) alike, and also based on the original story created by Falcom, Tonkinhouse’s Mega Drive version was later cancelled.
Both projects came to a head in 1993 when two separate versions of Ys IV, called "The Dawn of Ys" (Hudson, PC Engine) and "Mask of the Sun" (Tonkinhouse, Super Famicom), were released in Japan.
In addition, a third version of Ys IV was released twelve years later on the PS2 by Taito, based loosely on "Mask of the Sun." None of these games were ever released outside of Japan.
Each version of Ys IV takes place in the same basic setting, featuring many of the same characters, but is a distinctly different game from each of the other versions. Ys: Memories of Celceta is in many ways a remake of Ys IV, though Falcom officially regards it as an original title -- and even more so than its three predecessors, this distinction seems wholly appropriate, as Ys: Memories of Celceta boasts the biggest changes in story, presentation, gameplay and even music out of every Ys IV to date. It seems only fitting, then, that no numeral be placed in its title; this is not Ys IV: Memories of Celceta, but rather its own entirely unique entry in this quarter-century-old series. It’s best to think of it as a different account or interpretation of the same events.
None of the prior versions of Ys IV need to be played in order to enjoy Ys: Memories of Celceta, but there are plenty of references to them scattered throughout for die-hard series fans. Some are significant, while others are extremely subtle. Ys fiends would do well to try finding them all!