Byakuren

The was the one who founded Kirigakure in the Land of Water.

Background
At the first meeting of the five Kage, the First was accompanied by a shinobi from his village. He sat alongside the others, and told Hashirama Senju that if he acted so humbly as to bow to them — his equals — he would suspect an ulterior motive for having them gather in such a manner. He later expressed outrage when the First Kazekage made a demand that instead of receiving a tailed beast — as the sand priests of Sunagakure had already sealed away one — they requested 30% of whatever the other nations would pay for a tailed beast from Konoha, claiming the amount to be too high a demand. As infighting broke out and Hashirama made his plea to them to preserve the future of their children and unite, he looked on thoughtfully at the proceedings.

Personality
While much was not seen of his personality, he seemed to be cautious in nature while being a frank person, mincing no words with the First Kazekage when he showed no signs of lowering or abandoning his conditions for signing the treaty, and noting that if Sunagakure were to plan to attack them, the other nations could band together and destroy them. His cautious nature was also displayed with Hashirama when the latter was acting too humble over the five Kage meeting for his liking, going as far as suggesting that Hashirama had a hidden agenda for the meeting.

Appearance
In his old age, the First had copious amounts of long, grey hair along with a long moustache, and beard that merged into one all of which almost covered the entirety of his face. He had a scar that ran across his left eye — which was a different colour than his right eye. His teeth were sharp and triangular; a trait carried by generations of shinobi from Kirigakure. Attire-wise, he wore a simple, light-coloured, loose-fitting kimono over a pair of dark pants. His right eye is black and his left eye is pure white.

Infinite Tsukuyomi Arc
Subsequent to Kaguya Ōtsutsuki being sealed by Naruto Uzumaki and Sasuke Uchiha, he and the other deceased Kage were summoned from the Pure Land by Hagoromo Ōtsutsuki to aid him and the Hokage in summoning Team 7, the tailed beasts and Madara Uchiha's discarded corpse from Kaguya's dimension.

Trivia

 * In his anime debút during Hashirama Senju's speech about the creation of the Five Great Shinobi Countries, his eyes are depicted as being the same colour.