Please watch this 30 minute movie.
The real story was leaked long ago thanks to interviews, trailers, screenshots.
The beginning is actually just your classic RPG, start in a town, learn to fight, play with young Noctis, happy moments with Regis and Iris, even do soccer (there is a soccer field in the game's files).
Stella, Noctis actually died once already when they were young, Lupus stayed alive, but he can not see.
Etro made a miracle happen but in turn she lost her powers and fell in a deep slumber.
Stella and Noctis marked as l'Cie and lose their memories, if they fulfil their focus, they die.
After the accident, fast forward time.
Noctis Lucis Caelum is in his car, heading to Nihilsomno tower.
He meets with Stella, though they do not remember each other.
The invasion starts and the Hooded Man is actually an anti-hero, he communicates using Gentiana (Pryna) staying in the shadows.
Lupus Nox Fleuret has a false prophecy and sends out Glauca to assassinate Regis, fails, because he doesn't know about the ring.
Regis tells Noctis that he never will be king.
He is forced to retreat to Altissia.
The Crystals are actually Crystals of Light and when the last light is destroyed, the land will be overthrown in Chaos.
Lupus Nox Fleuret is actually trying to channel energy into the Crystal to keep it from depleting.
His focus is to protect the Crystal and joins Safay Roth as a spy to inform and get advice from Gentiana and lead Stella and Noctis closer to their focus.
Safay Roth actually knows this and intercepts Pryna, leading Noctis Lucis Caelum to actually murder Stella Nox Fleuret.
Lupus Nox Fleuret becomes enemies with Noctis Lucis Caelum and abandons his focus, turning into a c'ieth later on.
Noctis Lucis Caelum loses his power, his father, his kingdom, his beloved childhood friend Stella.
In Altissia, Prompto figures out that his father is Verstael and cannot fight anymore.
Gladiolus did knot know that his father Clarus Amicitia died when protecting Regis, and finds the Lucis Caelum family unworthy of their protection.
Lupus betrays the Lucis Caelum family and steals the ring, leaving Regis powerless and is then murdered by Leviathan / Safay Roth.
Ignis stays loyal but he gets blinded when trying to use the ring, trying to save powerless Noctis.
During his slumber, he communicates with his ancestors.
Noctis learns that the ring is a gift from Etro and allows the bearer to summon weapons and Eidolons from the Dead, hence those crystals floating.
The eidolons are actually spirits of long forgotten dead ancestors themselves, Shiva is Gentiana (dog that died, who can transform into a human) who wants to vow revenge on Safay Roth.
Noctis father actually loved him and didn't want him to use the ring because it would take his life.
Everyone thinks Noctis is done for good, as he returns back with new powers.
Safay Roth wants to open Etro's gate and own the throne.
He succeeds and the final battle is in the Heaven, with all the chosen dead characters siding with Noctis and fighting him.
Etro wakes up as dawn returns while she restores the Crystals to their former glory.
Noctis and Stella on the throne in Heaven, end of story.
In the end, Noctis and Stella themselves were actually "summons", referencing to FINAL FANTASY X'S tragedical ending.