For nearly 300 years, the three kingdoms of the Carectia Peninsula have been locked in a series of exhausting territorial wars.
Following a peace treaty aimed at rebuilding the nations and restoring peace, two individuals once hailed as “war heroes”—the Archmage Yures and his companion, the swordsman Karca—have settled in a forest near a small village far from the kingdom’s capital. Yures suffers from agoraphobia, and Karca worries about him. One day, as the two were living their quiet lives, a young brother and sister who had gotten lost in the forest burst into their home. But soon, Yures discovers a strange pattern on the back of the children’s necks…(Source: Ridibooks, translated)
— Description from AniList community (anilist.co).
