Fire Emblem: Three Houses (Nintendo Cinematic Universe)

Fire Emblem: Three Houses is a Japanese anime film.

Summary
After recovering from a five-year coma, Byleth, a professor of Officers Academy, becomes entangled in a war that was instigated by his/her classmates and their kingdoms.

Verdant Wind
Byleth sides with the Golden Deer.

Azure Moon
Byleth sides with the Blue Lions.

Crimson Flower
Byleth sides with the Black Eagles.

Silver Snow
Byleth sides with the Church of Seiros.

Plot Elements

 * One night, Byleth and Jeralt rescue three young nobles, Edelgard, Dimitri, and Claude from bandits, greatly impressing them. During the attack, Byleth is saved by the mysterious Sothis, who remains within them.
 * Jeralt and Byleth are summoned to Garreg Mach Monastery, the home of the Church of Seiros, Fódlan's dominant religion.
 * Jeralt reluctantly rejoins the Church's military arm, the Knights of Seiros, while Byleth is made a professor of the monastery's Officers Academy. Jeralt privately warns Byleth not to trust the Church's archbishop, Rhea.
 * Byleth is then given the choice of leading one of the academy's three houses: the Black Eagles, the Blue Lions, or the Golden Deer, each populated by students from the Empire, Kingdom, and Alliance respectively.
 * Byleth assumes their duties as teacher for their chosen house, training their students and leading them in battles on behalf of the Knights of Seiros.
 * Byleth and their students discover frightening hints on the nature of Relics and Crests, such as a Relic thief transforming into a monster. Various conspiracies meddle with the monastery and plot against the Church: masked warriors called the Flame Emperor and the Death Knight, the Western branch of the Church, and a hostile cult known as "those who slither in the dark".
 * Byleth thwarts an attempt to steal a powerful Hero's Relic, the Sword of the Creator. Unexpectedly, the Sword activates when Byleth holds it, and Rhea allows them to keep it.
 * Jeralt is murdered by an agent of "those who slither in the dark".
 * Reading Jeralt's diary, Byleth discovers that Jeralt fled from the Church due to Rhea's plans for Byleth when they were born.
 * The "Sothis" within Byleth is the original Progenitor God, implanted by Rhea into Byleth as a baby so that Sothis would be reborn.
 * Byleth pursues the cultists responsible for Jeralt's death.
 * A magical attack by one of their leaders forces Sothis to merge with Byleth, allowing them to survive and defeat the cult members with a newly empowered Sword of the Creator.
 * Rhea makes a futile attempt to awaken Sothis within Byleth, but the Flame Emperor attacks the ceremony with allies from the Adrestian Empire.
 * The Flame Emperor is revealed to be Edelgard, who like Byleth bears the Crest of Flames; she accuses the Church of being corrupt; Rhea is also revealed to be a dragon.
 * Byleth is knocked unconscious at the end of the battle and wakes up five years later, discovering that Fódlan has plunged into war as the Empire, Kingdom, Alliance, and Church battle each other.

Verdant Wind

 * Byleth reunites with Claude, and they rally their students and the remnants of the Church to stand against the Empire.
 * Gathering allies and support, Byleth and Claude invade the Empire. As they confront Emperor Edelgard and her forces, a Kingdom army led by Dimitri also arrives, resulting in a massive battle. Edelgard is forced to retreat while Dimitri is killed.
 * Byleth and Claude press on towards a strategic Empire fort, and receive aid from the foreign nation of Alymra.
 * Claude admits he secretly opened relations with Almyra, and announces his desire to open Fódlan's borders to the outside world and end the continent's isolationism.
 * Byleth and Claude attack the Empire capital, where they defeat and kill Edelgard.
 * Byleth and Claude learn "those who slither in the dark" have been manipulating both the current war and the original original war a millennium before.
 * Claude's army defeats the cult in their secret underground city Shambhala. Their leader attempts to destroy them with a rain of missiles, but Rhea intercepts the missiles in her dragon form. Meanwhile, Nemesis is awakened from his tomb by the cult; he and his Ten Elites were a band of thieves who took power from Sothis and her dragon kin after they were slain by the cult in the ancient era. This power was the source of the nobility's crests.
 * Byleth and Claude destroy Nemesis and his undead army.
 * In the aftermath, Fódlan is united under the rule of Byleth and Claude as they open its borders and start relations with foreign nations.

Azure Moon

 * Byleth reunites with Dimitri, who has been ousted from the Kingdom due to a coup from pro-Empire nobles. Dimitri has become bitter, disillusioned, and unstable as he is haunted by visions of his deceased family and driven to kill Edelgard at any cost.
 * Byleth's students and the remnants of the Church ally with Dimitri despite his erratic behavior.
 * Dimitri eventually forces a massive battle between his own army, the Empire, and the Alliance, resulting in heavy losses on all sides.
 * One of Dimitri's trusted vassals sacrifices himself to protect him from an assassin, which combined with Byleth's guidance causes Dimitri to abandon his desire for revenge.
 * After securing his own lands, Dimitri rescues Claude from imperial forces.
 * Claude dissolves the Alliance and cedes its lands to Dimitri before departing Fódlan.
 * Dimitri then marches for the Empire capital itself.
 * Wanting to make peace with Edelgard, Dimitri arranges a meeting with her and suggest they join forces to realize their goals; Edelgard refuses.
 * Dimitri is able to defeat Edelgard and once again offers her mercy, but is forced to kill her when she attempts to attack him.
 * In the aftermath, Fódlan is united under the Kingdom with Dimitri as its ruler, while Byleth becomes the new archbishop of the Church when Rhea steps down.

Crimson Flower

 * Siding with Edelgard, Byleth reunites with their students and finds that the Kingdom has allied with the Church while the Alliance remains nominally neutral.
 * Edelgard and Byleth attack and seize the Alliance capital and eliminate Claude from the war, either through killing or exiling him. They then advance into the Kingdom, taking a vital fortress.
 * In retribution for Edelgard interfering with their schemes, "those who slither in the dark" arrange for the fortress to be destroyed.
 * Edelgard keeps the truth a secret and tells the others that the fortress was destroyed by Church weaponry.
 * Edelgard continues to lead her armies to the Kingdom's capital.
 * Dimitri meets Edelgard in battle, but is defeated and killed.
 * The Kingdom army is routed and Rhea withdraws to the Kingdom capital with her Knights.
 * In her madness, Rhea sets fire to the city, forcing Edelgard to attack to put a stop to her. Byleth and Edelgard are able to kill Rhea.
 * Byleth nearly dies, but Sothis's Crest Stone embedded in their heart dissolves, reviving them.
 * In the aftermath, Edelgard unites all of Fódlan under the Empire and abolishes both the Church and the nobility.

Silver Snow

 * Byleth sides with Church remnants and the Black Eagle students against the Empire.
 * After defeating Edelgard in the Empire's capital and "those who slither in the dark" in Shambhala, Byleth learns the full truth of their origins from Rhea, and is then forced to defeat her after she is driven berserk due to wounds sustained in Shambhala.
 * Fódlan is subsequently unified under the Church with Byleth as its new leader.

Ending

 * Mid-Credits Scene: Shortly after Byleth after falls into a coma, some members of the three houses disintegrate into golden dust particles.