Sumeragi is the deceased king of Hoshido. He is the father of Ryoma, Hinoka, Takumi, and Sakura through his first wife, Ikona, and the stepfather of the Avatar by marrying Mikoto. He also is the paternal grandfather of Shiro and Kiragi.
Prior to the events of Fates, Garon called Sumeragi to Cheve to discuss negotiation terms due to the war between Hoshido and Nohr. Sumeragi took the Avatar with them, believing that Garon was willing to end the war. When he arrived, Garon revealed to him that it was a trap, and ordered his soldiers to attack. Sumeragi sacrificed himself so that the Avatar would be protected from the barrage of arrows, then was finished by Garon.