Professor Ryoma Sengoku (プロフェッサー 戦極 凌馬, Purofessā Sengoku Ryōma), is one of the major antagonist of Kamen Rider Gaim alongside Redyue. He was the head of Yggdrasill Corporation R&D and the inventor of both the Sengoku Driver and Genesis Driver who transforms into Kamen Rider Duke (仮面ライダーデューク, Kamen Raidā Dyūku). After his demise, he is temporarily revived by Megahex.