"Eternal Calm" is also the name of a prequel FMV to Final Fantasy X-2, which was included with the release of Final Fantasy X International and Unlimited Saga and through the Official U.S. PlayStation Magazine. This FMV is also called Another Story in some languages. The movie shows Yuna trying to relax and enjoy her life after defeating Sin. She is shown practicing holding her breath for extended periods of time in order to play blitzball, her best time being 2 minutes and 41 seconds. She also has meetings with different people from all over Spira who wish to receive advice from the High Summoner; this seems to irritate Rikku, as Yuna is still putting her life on hold for others.
At the beginning of the Eternal Calm, Yevon has collapsed, causing chaos throughout Spira, especially in Bevelle, the former heart of Yevon. Due to the collapse of Yevon, a political void is created in Spira, which opens up to various new groups such as the Youth League, New Yevon, and the Machine Faction. As the Machine Faction is the only neutral group, members from the Youth League and New Yevon want Yuna to join, but she refuses to join any group.
During one of her visits to Besaid, Rikku shows Yuna a sphere of someone bearing an uncanny likeness to Tidus jailed in Bevelle. Yuna decides to join Rikku's sphere hunting group to search for him, leading to the beginning of Final Fantasy X-2. Rikku determines Yuna needs to travel incognito and provides her with her new outfit for their journey.
The teachings of Yevon are seen to be false, and during Final Fantasy X-2's story, the player can witness how some temples have been abandoned completely, such as Djose Temple (now being used as the Machine Faction's Headquarters). Also, the player can see the wide introduction of machina throughout Spira, allowing the Al Bhed to finally step out and be accepted by many citizens of Spira. The Al Bhed help Spira rebuild after a thousand years of tyranny from Sin and anti-machina teachings of Yevon, but instead of being "imitative" and copying ideas from the past, they started to become more "innovative", creating fresh ideas that were adapted to the situation at the time.
- The developers didn't initially plan on making a sequel for Final Fantasy X, but due to the strong fan reaction Eternal Calm received when it was released along with Final Fantasy X: International, they decided to continue the story.
- Interestingly, since Eternal Calm takes place two years after Final Fantasy X, Rikku looks exactly the same; though this can be explained by the fact that the developers weren't initially planning on making Final Fantasy X-2 at the time, so Rikku wouldn't have had a new character model as she did in X-2.
- There is a difference in the video Rikku shows Yuna in the Japanese version. In the original Japanese version of the video, Tidus is the one shown inside the Bevelle prison instead of Shuyin. This was changed in the English version.