Eleven years before the resurrection of the serpent, a monster that awakens once every three hundred years. There were those who aspired to protect the nation from the shadows of history. They were the Yamainu, a unit formed to slay the serpent. Serving as the instructor for this unit, led by the head of the Kumon family, Taiko, were not only Tenka but also his allies, Abe Aose and Sasaki Hiko. However, due to a certain incident, Tenka would part ways with the Yamainu, who shared his aspirations. Because there were things he could not protect while remaining a member of the unit—. In the twelfth year of the Meiji era. With the serpent vanquished, under the clear skies of Shiga, the Yamainu and the Kumon brothers come to understand Tenka's hidden feelings.