Kokuraı1

Kokurai might not be one of the people you except from a typical gijinka. He does not have a gender, even though Kokurai prefers to be called a "he." It all happened from a war between the twin brothers, who could not decide between truth and ideals, causing the once powerful dragon to become unstable and split into two entities, Kokurai and Shirohi, hence the reason why both of the separated dragons does not have a gender. In the end, Kokurai was a guardian for the Hero of Ideals, and was ordered to fight his twin dragon. But neither could defeat each other and it resulted in Unova being destroyed with their powers disappearing due to exhaustion. Not long after, their bodies' were destroyed and reverted to their respective stones

Thousand years later… The story changed and eventually passed as a mere legend. The stones came to existence once again when both Dark Stone and Light Stone were excavated to Clay and passed to Lenora. Only the Dark Stone was made public, which would later be stolen by Team Plasma for N to awaken Kokurai, in his Pokemon form. However, it took N a while to become the Hero of Ideals because Kokurai did not take the thousand year long slumber lightly.

Once the Light Stone was assumed to be awakened by Black, when Kokurai was finally reunited with Shirohi, he was immediately reminded of the events that happened over a thousand year ago because of the fact they had to engage in a battle between two of them. Ultimately, Shirohi became the victor.