Takeo Doi (土井 武夫, Doi Takeo; 31 October 1904 – 24 December 1996) was a Japanese aircraft designer. He designed many World War II fighter aircraft used by the Imperial Japanese Army Air Force. His most important work was the "Army Type 3 Fighter" (三式戦闘機, Sanshiki sentoki), a.k.a. Kawasaki Ki-61 "Hien" (飛燕, Hi-en) ("flying swallow") or "Tony". Also he was one of the chief designers of the Nihon Aircraft Manufacturing Corporation (NAMC) YS-11.
Source: “Takeo Doi (aircraft designer)”, English Wikipedia (CC BY-SA 4.0), excerpt