Riku was an 18 years old Imanity who lived during the Great War on Disboard. He was one of the main protagonists in Tet's story. He encountered Shuvi while going on an expedition and brought her to his colony after having lost in a game against her (albeit willingly).
He bears many similarities with Sora, being his black hair, slender body, black eyes and his face. Riku is a master strategist and manipulator, much like Sora. He is capable of duping even the matriarch of the Nilvalen family (known as the strongest and smartest Elf at the time) into giving out valuable information, albeit at the cost of his health.
(Source: No Game No Life Wikia)
