The Legend of Heroes: Trails into Reverie/Recollection of the Witches

Recollection of the Witches (魔女たちの追憶 ) is an episode in. Its events take place prior to the main story.

Background
The episode can be accessed from the Infinity Corridor.

Synopsis
In Eryn, Emma Millstein is contemplating her future; the death of her mother and that everyone is leaving her for faraway places. She is beckoned to wake up by a strange voice, ready to learn the truth. She was in Roselia's room, where she finds a strange journal. The journal is from her mother, Isola Millstein.

After the war, Emma and Celine were sent across Erebonia to make sure that the Septium veins were finally at peace. With the veins back to normal, they had returned to Eryn to report it to Roselia. Back to the present, Emma confronts Roselia over the journal. Vita Clotilde then teleports in, having sensed some interesting casuality. Vita states that it is Isola's journal and that Roselia knows where Isola lost her life.

Roselia admits defeat and states that when Emma enrolled into Thors Military Academy, an owl came to Eryn with the journal and the note. The note said to give the journal to Emma when the time came. Vita states that it was how witches communicated in the Middle Ages and recalls Isola's familiar was a white owl, but Roselia states that it wasn't hers. The journal is empty, but can be filled by finding the truth. However, none of them know where to start when Zeit walks in. Roselia is surprised to see Zeit, as she believed he was still fulfilling his duties as one of the Holy Beasts. Zeit states that with the war ended in Crossbell, he has some time to wander around and states that he found something intriguing in Osgiliath Basin.

Upon finishing their preparations, the five teleport to the basin where they find a massive, white Spirit Shrine. Zeit leaves the group, so the witches and Celine enter. The Shrine contains Isola's memories which can be unlocked after completing trials by defeating various monsters. As they clear the enemies, the journal begins filling up. Isola states that she has sensed a black that the others have not. Believing it to be the work of the Gnomes, and knowing that an all-out war between the two groups would be fatal, chose to go alone to investigate. Roselia remarks that Isola was one of her best students.

As they continue defeating more monsters, Isola states that she has to destroy Alberich, a subordinate of the black who had possessed the body of a Gnome. Unless she destroyed him, he would continually come back in another vessel. This fight resulted in both losing their lives, but Isola's attempts were in vain as Alberich eventually moved into Franz, Alisa's father. With all the monsters cleared, Emma soon resonates with Isola's owl. Isola states that she is proud of her daughter's growth, seeing her as Erebonia's future. She apologizes to Roselia for doing things on her own and hopes she lives a long life. Isola then notices Vita and tells her that there are more people who care for her, but she needs to watch her limits and that she wouldn't forgive her if she harmed Emma. Finally, she addresses Celine and thanks her for supporting Emma and the others.

Isola admits that she is curious about Emma's school and love life, hoping that she can enjoy a happy life of her own. She then disappears, causing the entire shrine to disappear too. The four end up in the basin once more. Roselia wonders what Isola meant in her final words. Emma asks Roselia if she can leave Erebonia to wander Zemuria, much to her surprise. Emma explains that there's more to learn about the outside world and she wants to protect everyone she holds dear, and that there are external threats too, such as McBurn being a resident of the Outside and the Azure Tree. Vita states that she'll support Emma's decision, as when she became an Anguis, she learned a lot about the world beyond Erebonia.

Roselia concedes, stating that their existence is now known by the outside world after the Great War. She knows that Emma will not abuse her magic like Vita, but warns her that she won't be able to cover for her outside of Erebonia. Celine states that she can do so, but Roselia states that she wouldn't be able to see Emma again. Emma states that she won't leave right away. Vita then leaves, reminding Roselia to keep a healthy diet. Roselia and Emma remark that Vita has changed, perhaps in the direction of her old self. The three then return to Eryn, where Emma is excited to uncover more of Roselia's secrets, which she vehemently denies.