Yuki Yuna Is a Hero: Hero History Apocrypha

The story of Nogi Wakaba wa Yuusha de Aru takes place 300 years in the past, in 2018, the first days of the Divine Era. The six main characters form the first ever Hero Team: Nogi Wakaba, Nogi Sonoko's ancestor; Uesato Hinata, Takashima Yuuna, Koori Chikage, Doi Tamako and Iyojima Anzu.

Includes:
Chapter 0: Ni-satsu-me no Yuusha Gyoki (The Second Hero Diary)
Volume 1 extra chapter: Shiratori Utano wa Yuusha de Aru (Shiratori Utano is a Hero)
Volume 2 extra chapter: Takusareta Baton (The Passed Baton)

A short side-story during the events of Nogi Wakaba wa Yuusha de Aru, centered on Uesato Hinata.

300 years ago, in the background of the first Heroes who fought against the Vertexes when the world was still in the Christian Era, there was another battle for the Mikos led by Uesato Hinata.

Hero History Apocrypha (勇者史外典) part 2 of 3.

In year 29 of the Divine Era, more than thirty years have passed since a mysterious monster from the heavens destroyed all of Japan except Shikoku. Young boys and girls, already unaware of the tragedy of that time, live in peace behind the wall that protect Shikoku. In such a time, there was a girl who was given the name "Yuuna" because of a special gesture she made at birth. Yuuna is an honorary name taken from Takashima Yuuna who perished in a fierce battle with the monsters about 30 years ago. Yuzuki Yuuna was one of those Yuunas, but contrary to her heroic name, she was a girl with no special powers. She learns that there is a girl in the same school with the same Yuuna name. Fuyou Lilienthal Yuuna — She says, "My dream is to go outside the wall and see the world for what it really is."

Hero History Apocrypha (勇者史外典) part 3 of 3.

It's the summer of 2015, 300 years before the time of the TV anime "Yuuki Yuuna wa Yuusha de Aru", and "that day" when humanity was destroyed.

One of the first Heroes, Takashima Yuuna, has been shrouded in mystery until now, except for the fact that she is from Nara Prefecture.
Where did she awaken to her Hero powers, how did she end up in Shikoku, and how did she become a Hero?

The story is finally told in the memoirs of Karasuma Kumiko, who is said to be the miko who discovered Takashima Yuuna.