No Game No Life Chapter 2: Eastern Union, Vol. 1 (manga) — Yuu Kamiya

A world governed entirely by games does not favor a timid, powerless race like Immanity, but it's perfect for a pair of legendary shut-in gamers! Sora and Shiro are now king and queen of Elkia, the last bastion of Immanity. But saving a kingdom is no small task, and responsibility isn't a game either sibling claims to have a high score in… Good thing the allure of more challenging contests (and sexy animal women) is all the motivation they need to set their sights on a new conquest -- Immanity's powerful neighbor, the Eastern Union!