81 Produce stated that his family had already held funeral services him. The agency did not mention a cause of death.
Some of Kawakubo's more prominent anime roles include Guame in Gurren Lagann, Kevin Yeegar in D.Gray-man, Quincy in Bubblegum Crisis and Scramble Wars, Grospoliner in Silent Möbius, Lord Haizen in Slayers Great, Admiral Dhorasoo in Gunbuster 2: Diebuster, Michael in Iruka to Shonen, and Old man in The Cherry Tree. He also voiced smaller roles in such anime as Golgo 13, Cyborg 009, Kimba the White Lion, Star Blazers: The Bolar Wars, Trigun, Sindbad the Sailor, Paranoia Agent, The Legend of the Galactic Heroes, and Salaryman Kintaro, among many others.
Kawakubo also voiced many dub roles, including Prince John in Disney's Robin Hood film and Edgar the Butler in Disney's The Aristocats film. He also voiced Godfrey Tibbett in the dub of the A View to a Kill film. He was also known for his work in narration.
Image via 81 Produce