No Game No Life, Vol. 4 (light novel)

"Having been transported to the world of Disboard, where everything is decided by games, Sora and Shiro (who together form the unstoppable gamer team " ") are still winning. They've racked up an unbroken string of victories against opponents armed with all manner of magic and treachery. As the pair enjoy a well-deserved vacation in the Eastern Union, they're approached by a Dhampir named Plum. Sora and Shiro prepare for battle, but this game is one of the very few they haven't beaten and mastered--the game of love!"--Amazon.com.