No Game No Life, Vol. 9 (light novel)

Gamer siblings Sora and Shiro have at last defeated the Old Deus Holou, and now they're switching gears: their next endeavor is to make Holou the number-one idol pop star in all of Disboard! But amid the chaos of their pet project comes a strange message from the representative of the 10th-ranked race, the Ex Machina... Is another arduous battle on the horizon for Sora and Shiro?!