A (エー, Ē, Viz: Ei, English TV: Ay) was the First Raikage (初代雷影, Shodai Raikage, Literally meaning: First or Founding Lightning Shadow) who founded Kumogakure in the Land of Lightning.
During his leadership in the early days of Kumogakure after the Warring States Period, A presumably sent the Gold and Silver Brothers to capture the Nine-Tails, a task at which they ultimately failed. He also gave land in the Valley of Clouds and Lightning to the Yotsuki Clan in return for their loyalty.
At the first meeting of the five Kage during the First Shinobi World War, he was accompanied by the future Second Raikage; his long-time bodyguard. He sat alongside the other Kage and told Hashirama that bowing to other Kage was not a sign of a lasting leader. After asking the First Kazekage to give voice to his alternative request, since Sunagakure already had a tailed beast, he expressed outrage when the Kazekage made a demand of receiving 30% of whatever they would pay for a tailed beast from Konoha. As infighting broke out and Hashirama Senju made his plea to them to preserve the future of their children and unite, he looked on intently.
Before his death during the war, A would leave a strong moral mark related to his desire to protect Kumogakure in his bodyguard, whose long service and dedication earned him the nomination as his successor.