Kamiya, Yuu: No Game No Life, Vol. 6 (Light Novel)

Before Sora and Shiro set foot on Disboard, there was another remarkable duo!!Tet, the One True God, takes a break to amuse himself among the mortals only to collapse on the streets of Elkia. When a familiar face finds him and lends a helping hand, the God of Play regales her with a tale from the Great War about a human man who challenged the world and a strange girl who sought to comprehend the human heart...Let the games begin!