Kōga Gengo (甲賀源吾, "Gengo Kōga", February 16, 1839 - May 6, 1869) is a Japanese samurai from the Kakegawa Domain and a Bakushin, mean that a samurai who serves under direct rule lord of the Shogun. He was a boarding captain during the Boshin War and commanded the paddle corvette "Kaiten" where he is killed during the Battle of Miyako Bay. 