Heirs of Fate (泡沫の記憶編, Utakata no Kioku Hen lit. Transient Memories Compilation in the Japanese version) Xenologue 15 in Fire Emblem Fates, released in March 2016 in Japan, May 2016 in North America and July 2016 in Europe.
It is similar to The Future Past series from Awakening, where in another dimension, after the war ended, mysterious invaders started attacking the Deeprealms. The children's parents fought to protect them, although their fate is unknown. Shiro, Kiragi, Forrest, Siegbert, and two Kanas inherit and wield their parents' weapons. Shigure narrates the story, which consists of six chapters.
In the first Xenologue, female Kana is crying at the fact that she was not strong enough to fight alongside her father, and fears that he may have been killed. She bumps into Mitama and Selkie, who are experiencing the same problems like her. While conversing, the three are ambushed by invisible soldiers and decide to retreat, as they are outmatched. They soon find Kiragi and Hisame fighting off two more of the invaders; Kiragi tries to attack them with the Fujin Yumi but continually misses because of his lack of experience with it. However, after enough tries, he manages to kill both of them.
The three then converse with them, and suddenly, the Fujin Yumi starts reacting with the Yato. It turns into the Noble Yato, and Kana is able to fight back against the invaders. The children later take the fight to the invaders, where they meet a large group but defeat them in battle. After the battle, one invader flees from the battlefield; Kana starts chasing them when a spirit appears before her, telling her not to. Kana, Mitama and Selkie somewhat recognize but are unable to properly identify the spirit. The spirit notices Kana's Yato and explains the several forms of the Yato to her. She then asks her if she has ever turned into a dragon before; Kana tells her that she has never done so before. The spirit hands Kana a Dragonstone, explaining its uses to her before leaving.
Elsewhere, Shigure is busy singing and is aware of the task that he has to complete. In this portion, he sings the Birthright verse of Lost in Thoughts All Alone, where he notes that this is the path where the sakura (the cherry blossom) was chosen over the rose.
Dwyer and Sophie are busy trying to calm down male Kana who has turned into a dragon, to no avail. Elsewhere, Forrest, Nina and Ophelia are wandering around when they hear a dragon roar and find several invisible soldiers surrounding Kana. During the battle, the group manages to escape from a Vallite ambush, and Kana returns to normal. Kana reveals that invisible soldiers had attacked his parents, similar to the other children. Kana's Yato reacts with Forrest's Brynhildr, turning it into the Grim Yato. Suddenly, all of the children present, barring Kana, forget who Kana is, much to his confusion. However, Kana notices Azura's spirit, who gives him a dragonstone to control his impulses.
Elsewhere, Shigure is busy singing the Conquest verse of Lost in Thoughts All Alone. He notes that this is the path where the rose was chosen over the sakura.
Following the battle in Heirs of Fate 2, some of the Hoshidan children are badly injured. After a short argument where they reveal that their parents have also gone missing, invisible soldiers attack the children.
After the battle, the invisible soldiers regroup. Shiro attempts to attack, but is stopped by Asugi, who is later hurt by them. The invisible forces attempt to attack again, but Kiragi and female Kana enter and block their attacks. The Hoshidan children later retreat to a safer location. During this time, Shiro's Rajinto reacts with Kana's Noble Yato and turns it into the Blazing Yato. In high morale, the Hoshidan children continue on their way to bring the fight to the enemy.
Elsewhere, Shigure is busy singing the Revelation verse of Lost in Thoughts All Alone. Azura's spirit tells him that there is one last verse of the song he has to learn in order to save the world, but will likely cause him to disappear like she did.
After being defeated by some of the Hoshidan children, Siegbert and his group decide to stop and rest a bit. However, after some persuasion by Soleil, he decides to go to battle.
Elsewhere in a Deeprealm swamp, a group of Vallites chase after Forrest's group when they decide to retreat. As Forrest's group also leaves, Forrest spots Siegbert but hopes that he can hold them off. Siegbert thinks he saw Forrest, but unsure if his eyes were playing tricks on him, decides to press on.
At the Great Wall of Suzanoh, Siegbert and his group fight off the Vallites when Forrest and his group arrive. The two work together to question the invaders, eventually defeating them in battle.
After the battle, the Hoshidan children square off against the Nohrian children. Male Kana tries to fight back but his Grim Yato is not strong enough against female Kana's Blazing Yato. Siegbert offers Kana his assistance, and the Grim Yato reacts with Siegfried, turning it into the Shadow Yato. Kana uses it to attack female Kana, and for a few seconds, shows the true identity of both sides, confusing and surprising them before the illusion resets.
Both Kanas then turn into dragons. Siegbert and Forrest try to calm down male Kana, but are only stopped when Shigure steps in. The group finds themselves in Valla, and Shigure directs them to a safer location before telling them everything.
At the hideout, Shigure explains that Anankos had put an illusion spell on them in an attempt to kill each other after his first attempt to kill both parents and child failed. He starts to explain that both the Hoshidan and Nohrian children come from different realms, and tells them that they thought that they were all in one realm. Shiro and Siegbert comment on the war on their side and are surprised to hear what had happened; Shiro says the Hoshidans won the war and that Xander and Elise died (Birthright), while Siegbert says the Nohrians won and both Ryoma and Takumi died (Conquest).
Due to the conflicting stories, Shiro and Siegbert decide it is best to separate, much to Shigure's worry as rather than working together, they are refusing to just like Anankos had planned.
The group is now violently divided, with Shigure and the twin Kanas despairing over the divide: due to it, the Fire Emblem cannot be forged from either version of the Yato, making defeating Anankos seem an impossible task. Arete then attacks, separating the group and assaulting them with an army made up from the resurrected bodies of their older relatives. Each divided group is made up of one Nohrian and one Hoshidan, and the pair must work together to regroup. This done, Arete and her army is defeated, and the differences within the group dissolve.
Finally reaching Anankos' palace, the two Kanas attempt to evolve their respective Yatos into the Fire Emblem. Shigure then uses his song to sap the group's strength, declaring that the Yatos' final form will not be needed. Immobilized, the group learn the full truth from Shigure: rather than the two groups coming from two different realities, each member comes from their own reality where either Nohr or Hoshido was victorious, counter to Shigure's reality where they succeeded in forging an alliance. The alliance proved in vain, as Anankos broke free of his imprisonment and killed everyone but for Shigure and Azura, who gave her life to teach Shigure the key to defeating Anankos. Though triumphant, Anankos is wreaking havoc through other realities where he was still contained: the world's each group member come from have fallen into ruin under Anankos.
Shigure says that he merely needed the group so he could reach Anankos, then he would transport them outside the palace. He would then uses his powers to sing the fourth forbidden verse of his mother's song to seal himself and Anankos away from reality, enduring a fate worse than death to save all worlds from Anankos' madness. At first callously declaring them little more than strangers he used as tools, he transports them outside the palace after asking them to remember him as he will never leave Valla again, and voicing his gladness at being able to see and hear them once last time.
The group are now far away from Anankos' palace with no hope of getting back. As they discuss the problem, they remember advice given by Azura's spirit of how their memories could be used to save Shigure. Soleil and Ophelia realize that the stones given to them by their respective fathers Odin and Laslow years before were actually transport crystals similar to that used by Shigure. Using them, they transport back to Anankos' palace.
Inside the palace. Anankos and Shigure face each other, where the delusional Anankos mistakes Shigure for his ancient friend Cadros, and declares that the reason he invaded the Deeprealms was to find a world where humanity had not turned against him, so he could build a world where humans and dragons live in peace: Shigure declares this to be an impossibility, as Anankos has already gone mad. He begins singing the forbidden song, but then the Kanas' group intervenes, and reveals the key to saving Shigure: they offer up their memories as an alternate price for singing the final verse. Even though it will leave them with no memories of their time fighting together, they shrug off Shigure's objections and go ahead. The two Kanas then forge twin Fire Emblems, and go into battle against both Anankos and resurrected forms of each child's parents.
Defeated, Anankos regains his sanity through the song's power, and thanks Shigure for freeing him from the nightmare so he can join his brethren in the stars. Lilith appears to act as his guide on the journey. With Anankos gone from all the Deeprealm realities, the damage wrought to the Deeprealms is undone, and each child is able to return to their respective realms as if nothing had happened. Before everyone departs and loses their memories, Shigure fulfills his promise to Azura by tossing her pendant into the depths of a spring: the group, having faith that they will somehow remember, arrange a phrase they can use if they ever meet each other again - "It's good to meet you."
After promising to remember and love them all, Shigure tosses the pendant into the spring, its fall mimicking the opening screen of the game. In the post-credit scenes, each of the primary children are seen joyfully reuniting with their parents, while Shigure is at a house painting contentedly, watched over by Azura's spirit. A final scene shows the twin Kanas sitting together, and Shigure using the arranged greeting: what happens next is left unknown.