Knowing Tag

Knowing Tags are items each citizen of Dominion of Rubrum keeps upon their person that functions as their ID. The common folk maintain possession of their own Knowing Tags, but a special council is charged with keeping track of the Akademeia cadets' tags. As the Vermilion Bird Crystal removes the memories of the dead from the minds of the living, the Knowing Tag system allows the nation to keep track of the fallen. Even if no one remembers the deceased Akademeia has a cemetery for those lost in battle.

Story
After Izana Kunagiri is felled in the invasion of Akademeia by Militesi Empire forces, Ace picks up his Knowing Tag.